feat(drive): add drive policie

- add policy forbid_external_sharing
    - add policy forbid_sharing
    - add polocy forbid_cross_drive_move
    - add policy forbid_owner_role_change

src/domain/entities/drive.rs

@@ -43,6 +43,9 @@
 use serde::{Deserialize, Serialize};
 use uuid::Uuid;
 
+use crate::common::errors::DomainError;
+use crate::domain::services::authorization::Subject;
+
 /// Drive kind discriminant. Mirrors the `storage.drives.kind` CHECK
 /// constraint values.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
@@ -168,6 +171,16 @@ pub struct DrivePolicies {
     /// Blocks MOVE when `src.drive_id != dst.drive_id`. Enforced at the
     /// move endpoints. Lands paired with D6's cross-drive move work.
     pub forbid_cross_drive_move: bool,
+    /// Locks the Owner-role membership set: no owner can be added,
+    /// removed, or demoted by another owner — only OxiCloud admin can
+    /// change the Owner roster. Editor / Viewer mutations by remaining
+    /// owners are unaffected. Personal drives are already
+    /// single-owner-immutable via `refuse_if_personal`, so this policy
+    /// only adds value on shared drives. Enforced at
+    /// `DriveManagementService::set_member_role` (refuses Owner role
+    /// writes) and `::remove_member` (refuses Owner removals) when the
+    /// caller is non-admin.
+    pub forbid_owner_role_change: bool,
 }
 
 impl DrivePolicies {
@@ -179,4 +192,278 @@ impl DrivePolicies {
     pub fn from_value(value: &serde_json::Value) -> Self {
         serde_json::from_value(value.clone()).unwrap_or_default()
     }
+
+    /// D5 `forbid_public_links` gate, used by every entry point that
+    /// mints an anonymous token-share on a resource in this drive
+    /// (`share_service::create_shared_link` today; future protocol
+    /// surfaces — e.g. NextCloud OCS share — must call this too). The
+    /// gate owns the decision + audit + canonical error so the
+    /// rejection shape stays in lockstep across surfaces. See
+    /// `docs/plan/drive.md` §8.
+    ///
+    /// Returns `Ok(())` when the policy is off; emits a
+    /// `share.rejected` audit line and returns
+    /// `OperationNotSupported` when on.
+    pub fn refuse_public_links(&self, ctx: PublicLinkGateContext) -> Result<(), DomainError> {
+        if !self.forbid_public_links {
+            return Ok(());
+        }
+        tracing::info!(
+            target: "audit",
+            event = "share.rejected",
+            reason = "forbid_public_links",
+            caller_id = %ctx.caller_id,
+            item_type = ctx.item_type,
+            item_id = %ctx.item_id,
+            "👮🏻‍♂️ public-link creation refused: forbid_public_links",
+        );
+        Err(DomainError::operation_not_supported(
+            "Share",
+            "This drive does not allow public links.",
+        ))
+    }
+
+    /// D5 `forbid_sharing` gate: refuses **per-resource** grants on
+    /// resources in this drive when the policy is on. Drive-level
+    /// membership stays unaffected — otherwise a drive that disables
+    /// sharing would also become uneditable except by the original
+    /// owner. The semantic the plan §8 commits to is "no fine-grained
+    /// sharing of individual files; access happens through drive
+    /// membership only."
+    ///
+    /// Enforced at `grant_handler::create_grant` for File / Folder
+    /// resources. The Drive-resource branch of `/api/grants` and the
+    /// `/api/drives/{id}/members` routes deliberately don't call this
+    /// gate.
+    ///
+    /// Returns `Ok(())` when the policy is off; emits a
+    /// `grant.rejected` audit line and returns `OperationNotSupported`
+    /// when on.
+    pub fn refuse_sharing(&self, ctx: SharingGateContext) -> Result<(), DomainError> {
+        if !self.forbid_sharing {
+            return Ok(());
+        }
+        tracing::info!(
+            target: "audit",
+            event = "grant.rejected",
+            reason = "forbid_sharing",
+            caller_id = %ctx.caller_id,
+            resource_type = ctx.resource_type,
+            resource_id = %ctx.resource_id,
+            "👮🏻‍♂️ per-resource grant refused: forbid_sharing",
+        );
+        Err(DomainError::operation_not_supported(
+            "Grant",
+            "This drive does not allow per-resource sharing.",
+        ))
+    }
+
+    /// D5 `forbid_owner_role_change` gate: refuses Owner-role mutations
+    /// (adding a new Owner, demoting an existing Owner, or removing
+    /// one) when the caller isn't OxiCloud admin and the policy is on.
+    /// Membership of non-Owner roles is unaffected.
+    ///
+    /// Enforced at `DriveManagementService::set_member_role` (refuses
+    /// Owner role writes) and `::remove_member` (refuses removing an
+    /// Owner subject). Skipped when `caller_is_admin = true` — the
+    /// policy exists to constrain owners, not the tenant operator.
+    /// Personal drives never reach this gate because
+    /// `refuse_if_personal` rejects every member mutation upstream.
+    ///
+    /// Returns `Ok(())` when the policy is off or the caller is admin;
+    /// emits a `drive_membership.rejected` audit line and returns
+    /// `OperationNotSupported` otherwise.
+    pub fn refuse_owner_role_change(
+        &self,
+        ctx: OwnerRoleChangeGateContext,
+    ) -> Result<(), DomainError> {
+        if !self.forbid_owner_role_change {
+            return Ok(());
+        }
+        if ctx.caller_is_admin {
+            return Ok(());
+        }
+        tracing::info!(
+            target: "audit",
+            event = "drive_membership.rejected",
+            reason = "forbid_owner_role_change",
+            operation = ctx.operation,
+            caller_id = %ctx.caller_id,
+            drive_id = %ctx.drive_id,
+            subject_type = ctx.subject_type,
+            subject_id = %ctx.subject_id,
+            "👮🏻‍♂️ owner-role mutation refused: forbid_owner_role_change",
+        );
+        Err(DomainError::operation_not_supported(
+            "Drive",
+            "This drive's Owner membership is locked — only OxiCloud admin can change owners.",
+        ))
+    }
+
+    /// D5 `forbid_cross_drive_move` gate: refuses MOVE when
+    /// `src.drive_id != dst.drive_id`. The policy lives on the SOURCE
+    /// drive — its owner decides whether content can leave. Targets'
+    /// owners already gate inbound moves via the `Create` permission
+    /// on the destination folder, so a symmetric check would be
+    /// redundant.
+    ///
+    /// Enforced at `file_management_service::move_file_with_perms`
+    /// and `folder_service::move_folder_with_perms`. The handler
+    /// doesn't see this gate — it lives in the service layer per
+    /// the AuthZ architecture rule in CLAUDE.md.
+    ///
+    /// Returns `Ok(())` when the policy is off; emits a
+    /// `move.rejected` audit line and returns `OperationNotSupported`
+    /// when on.
+    pub fn refuse_cross_drive_move(
+        &self,
+        ctx: CrossDriveMoveGateContext,
+    ) -> Result<(), DomainError> {
+        if !self.forbid_cross_drive_move {
+            return Ok(());
+        }
+        tracing::info!(
+            target: "audit",
+            event = "move.rejected",
+            reason = "forbid_cross_drive_move",
+            caller_id = %ctx.caller_id,
+            resource_type = ctx.resource_type,
+            resource_id = %ctx.resource_id,
+            src_drive_id = %ctx.src_drive_id,
+            dst_drive_id = %ctx.dst_drive_id,
+            "👮🏻‍♂️ cross-drive move refused: forbid_cross_drive_move",
+        );
+        Err(DomainError::operation_not_supported(
+            "Move",
+            "This drive does not allow moving content out to another drive.",
+        ))
+    }
+
+    /// D5 `forbid_external_sharing` gate, shared by every entry point
+    /// that creates a grant on a resource in this drive
+    /// (`grant_handler::create_grant`,
+    /// `DriveManagementService::set_member_role`). Each caller
+    /// resolves `is_external` from whichever source naturally fits
+    /// (the just-created `User` entity in the email path, a
+    /// `get_user_flags` probe in the user-by-id path); the gate
+    /// itself owns the decision + audit + canonical error so the
+    /// shape stays in lockstep across surfaces. See `docs/plan/drive.md` §8.
+    ///
+    /// Returns `Ok(())` when the subject is allowed (policy off, subject
+    /// is not a User, or the User is not external). Returns
+    /// `OperationNotSupported` after emitting a `grant.rejected` audit
+    /// line otherwise.
+    pub fn refuse_external_sharing(
+        &self,
+        subject: Subject,
+        is_external: bool,
+        ctx: ExternalSharingGateContext,
+    ) -> Result<(), DomainError> {
+        if !self.forbid_external_sharing {
+            return Ok(());
+        }
+        let Subject::User(uid) = subject else {
+            return Ok(());
+        };
+        if !is_external {
+            return Ok(());
+        }
+        tracing::info!(
+            target: "audit",
+            event = "grant.rejected",
+            reason = "forbid_external_sharing",
+            stage = ctx.stage,
+            caller_id = %ctx.caller_id,
+            subject_id = %uid,
+            drive_id = ?ctx.drive_id,
+            resource_type = ?ctx.resource_type,
+            resource_id = ?ctx.resource_id,
+            "👮🏻‍♂️ grant refused: forbid_external_sharing",
+        );
+        Err(DomainError::operation_not_supported(
+            "Grant",
+            "This drive does not allow external sharing.",
+        ))
+    }
+}
+
+/// Audit / identity context for [`DrivePolicies::refuse_owner_role_change`].
+///
+/// Carries the subject (the user/group whose Owner status is being
+/// added, removed, or demoted) and the calling operation tag
+/// (`"set_member_role"` or `"remove_member"`) so the audit log
+/// pinpoints exactly which mutation the policy refused.
+#[derive(Debug, Clone, Copy)]
+pub struct OwnerRoleChangeGateContext {
+    pub caller_id: Uuid,
+    pub caller_is_admin: bool,
+    pub drive_id: Uuid,
+    pub operation: &'static str,
+    pub subject_type: &'static str,
+    pub subject_id: Uuid,
+}
+
+/// Audit / identity context for [`DrivePolicies::refuse_cross_drive_move`].
+///
+/// Carries the source and destination drive ids so the audit log
+/// captures exactly which boundary the refused move would cross —
+/// useful when investigating whether someone is probing the gate or
+/// genuinely trying to organize content.
+#[derive(Debug, Clone, Copy)]
+pub struct CrossDriveMoveGateContext {
+    pub caller_id: Uuid,
+    /// `"file"` or `"folder"`.
+    pub resource_type: &'static str,
+    pub resource_id: Uuid,
+    pub src_drive_id: Uuid,
+    pub dst_drive_id: Uuid,
+}
+
+/// Audit / identity context for [`DrivePolicies::refuse_sharing`].
+///
+/// Only File / Folder resources reach this gate — the per-resource
+/// grant surface. Drive-resource grants go through
+/// `set_member_role` and aren't subject to `forbid_sharing`.
+#[derive(Debug, Clone, Copy)]
+pub struct SharingGateContext {
+    pub caller_id: Uuid,
+    /// `"file"` or `"folder"`.
+    pub resource_type: &'static str,
+    pub resource_id: Uuid,
+}
+
+/// Audit / identity context for [`DrivePolicies::refuse_public_links`].
+///
+/// Single callsite today (`share_service::create_shared_link`), but the
+/// struct is the explicit contract so future surfaces (NextCloud OCS
+/// share, WebDAV public-link sigil, …) land with the same shape.
+#[derive(Debug, Clone, Copy)]
+pub struct PublicLinkGateContext {
+    pub caller_id: Uuid,
+    /// `"file"` or `"folder"` — the share target's resource kind.
+    pub item_type: &'static str,
+    pub item_id: Uuid,
+}
+
+/// Audit / identity context for [`DrivePolicies::refuse_external_sharing`].
+///
+/// Two callsites with different identifiers naturally fill this in:
+/// - `grant_handler` (File/Folder branch): `drive_id = None`,
+///   `resource_type` + `resource_id` set
+/// - `DriveManagementService::set_member_role`: `drive_id` set,
+///   `resource_type` + `resource_id = None`
+///
+/// All three appear in the audit log so a single grep on
+/// `grant.rejected reason=forbid_external_sharing` surfaces every
+/// refusal regardless of entry point.
+#[derive(Debug, Clone, Copy)]
+pub struct ExternalSharingGateContext {
+    pub caller_id: Uuid,
+    /// Distinguishes the call site for log aggregators. Known values
+    /// today: `"late_user"` (grant_handler), `"drive_member"`
+    /// (set_member_role). New entry points pick a fresh string.
+    pub stage: &'static str,
+    pub drive_id: Option<Uuid>,
+    pub resource_type: Option<&'static str>,
+    pub resource_id: Option<Uuid>,
 }