feat: user tombstone and retired usernames

crates/domain/src/testing/fakes/store.rs

@@ -59,6 +59,10 @@ pub struct InMemoryStore {
     pub(super) movie_profiles: RwLock<HashMap<Uuid, MovieProfile>>,
     pub(super) reviews: RwLock<HashMap<Uuid, Review>>,
     pub(super) users: RwLock<HashMap<Uuid, User>>,
+    /// Ids of `users` rows carrying a `deleted_at` tombstone.
+    pub(super) tombstoned: RwLock<std::collections::HashSet<Uuid>>,
+    /// Lower-cased `retired_usernames` (the column is NOCASE).
+    pub(super) retired_usernames: RwLock<std::collections::HashSet<String>>,
     pub(super) profile_fields: RwLock<HashMap<Uuid, Vec<ProfileField>>>,
     pub(super) user_settings: RwLock<HashMap<Uuid, UserSettings>>,
     pub(super) refresh_sessions: RwLock<Vec<RefreshSession>>,
@@ -82,6 +86,8 @@ impl InMemoryStore {
             movie_profiles: RwLock::default(),
             reviews: RwLock::default(),
             users: RwLock::default(),
+            tombstoned: RwLock::default(),
+            retired_usernames: RwLock::default(),
             profile_fields: RwLock::default(),
             user_settings: RwLock::default(),
             refresh_sessions: RwLock::default(),