feat: account deletion request and active-user check

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

@@ -78,13 +78,18 @@ impl UserRepository for InMemoryStore {
         events: &[crate::events::DomainEvent],
     ) -> Result<(), DomainError> {
         let id = user_id.value();
-        if let Some(user) = self.users.read().unwrap().get(&id) {
-            self.retired_usernames
-                .write()
-                .unwrap()
-                .insert(user.username().value().to_lowercase());
-            self.tombstoned.write().unwrap().insert(id);
-        }
+        let users = self.users.read().unwrap();
+        let mut gone = self.tombstoned.write().unwrap();
+        let Some(user) = users.get(&id).filter(|_| !gone.contains(&id)) else {
+            return Err(DomainError::NotFound("User not found".into()));
+        };
+        self.retired_usernames
+            .write()
+            .unwrap()
+            .insert(user.username().value().to_lowercase());
+        gone.insert(id);
+        drop(gone);
+        drop(users);
         self.refresh_sessions
             .write()
             .unwrap()