fix: resolve all clippy warnings and convert integration_tests to custom cfg

- Add type aliases (FileRow, FolderRow, FolderRowPaginated, FolderRowOptUser) to reduce type complexity
- Simplify redundant closures in app_password_handler and webdav_handler
- Remove needless borrow in auth_handler
- Collapse nested if/let chains in login_lockout, webdav_lock, auth, rate_limit
- Box LockEntry in acquire() Err variant to fix large enum variant warning
- Rename DeviceCodeStatus::from_str to parse to avoid should_implement_trait lint
- Add #[allow(clippy::too_many_arguments)] and #[allow(clippy::result_unit_err)] where appropriate
- Convert integration_tests from cargo feature to custom cfg attribute
- Add check-cfg lint config in Cargo.toml for integration_tests cfg

Cargo.toml

@@ -57,7 +57,9 @@ socket2 = { version = "0.6.2", features = ["all"] }
 [features]
 default = []
 test_utils = ["mockall"]
-integration_tests = []
+
+[lints.rust]
+unexpected_cfgs = { level = "warn", check-cfg = ['cfg(integration_tests)'] }
 
 [profile.release]
 lto = "fat"