✨(backend) persist user preferences for room defaults on the User model

Add attributes on the User model to persist per-user preferences for
the default link access level and the default room configuration.

The frontend will let users update these preferences and then reuse
them when generating a link through the webapp.

Persisting them on the backend (rather than in application memory
only) ensures the preferences survive across sessions and devices.

src/frontend/src/features/auth/api/ApiUser.ts

@@ -1,4 +1,8 @@
 import { BackendLanguage } from '@/utils/languages'
+import type {
+  ApiAccessLevel,
+  RoomConfiguration,
+} from '@/features/rooms/api/ApiRoom'
 
 export type ApiUser = {
   id: string
@@ -7,4 +11,6 @@ export type ApiUser = {
   last_name: string
   language: BackendLanguage
   timezone: string
+  default_room_access_level?: ApiAccessLevel | null
+  default_room_configuration?: RoomConfiguration | null
 }