feat(ui): add addressBook and systemUsers model + show person who shared an item with me in tooltip

static/js/model/systemUsers.js

@@ -0,0 +1,80 @@
+// @ts-check
+
+/**
+ * System-users convenience layer.
+ *
+ * Thin wrapper over `addressBook.listContacts(SYSTEM_BOOK_ID)` that
+ * provides a userId → display-name index.  Used wherever a grant's
+ * `granted_by` UUID needs to be shown as a human-readable name
+ * (owner tooltips, share dialogs, etc.).
+ *
+ * Falls back gracefully when the system address book is disabled
+ * server-side (`OXICLOUD_EXPOSE_SYSTEM_USERS` not set): `isAvailable()`
+ * returns false and `getDisplayName()` returns a shortened UUID.
+ */
+
+/** @import {ContactItem} from '../core/types.js' */
+
+import { addressBook, SYSTEM_BOOK_ID } from './addressBook.js';
+
+/** @type {Map<string, string> | null} userId → display name, built lazily */
+let _index = null;
+
+/**
+ * Derive the best human-readable name from a contact.
+ * Priority: "First Last" → full_name → primary email → shortened id.
+ * @param {ContactItem} c
+ * @returns {string}
+ */
+function _nameFor(c) {
+    const parts = /** @type {string[]} */ ([c.first_name, c.last_name].filter(Boolean));
+    if (parts.length) return parts.join(' ');
+    if (c.full_name) return c.full_name;
+    const mail = c.email?.find((e) => e.is_primary)?.email ?? c.email?.[0]?.email;
+    if (mail) return mail;
+    return `${c.id.slice(0, 8)}…`;
+}
+
+/**
+ * Ensure the index is built (idempotent).
+ * @returns {Promise<void>}
+ */
+async function _ensureIndex() {
+    if (_index !== null) return;
+    const contacts = await addressBook.listContacts(SYSTEM_BOOK_ID);
+    _index = new Map(contacts.map((c) => [c.id, _nameFor(c)]));
+}
+
+// ── Public API ────────────────────────────────────────────────────────────────
+
+/**
+ * Start loading the system address book in the background.
+ * Safe to call multiple times — subsequent calls are no-ops once loaded.
+ */
+function prefetch() {
+    if (!addressBook.isSystemAvailable()) return;
+    _ensureIndex(); // intentionally fire-and-forget
+}
+
+/**
+ * Resolve a user UUID to a display name.
+ * Awaits the first load if not yet cached; subsequent calls resolve instantly.
+ *
+ * @param {string} userId
+ * @returns {Promise<string>}
+ */
+async function getDisplayName(userId) {
+    await _ensureIndex();
+    return _index?.get(userId) ?? `${userId.slice(0, 8)}…`;
+}
+
+/**
+ * Returns `false` only after a confirmed 404 from the server (feature
+ * disabled).  Returns `true` when status is unknown or the book loaded OK.
+ * @returns {boolean}
+ */
+function isAvailable() {
+    return addressBook.isSystemAvailable();
+}
+
+export const systemUsers = { prefetch, getDisplayName, isAvailable };