feat(chats): add per-user pinned chats and pinned sorting

app/chats/service.py

@@ -64,6 +64,7 @@ async def serialize_chat_for_user(db: AsyncSession, *, user_id: int, chat: Chat)
     unread_count = await repository.get_unread_count_for_chat(db, chat_id=chat.id, user_id=user_id)
     user_setting = await repository.get_chat_user_setting(db, chat_id=chat.id, user_id=user_id)
     archived = bool(user_setting and user_setting.archived)
+    pinned = bool(user_setting and user_setting.pinned)
 
     return ChatRead.model_validate(
         {
@@ -77,6 +78,7 @@ async def serialize_chat_for_user(db: AsyncSession, *, user_id: int, chat: Chat)
             "is_public": chat.is_public,
             "is_saved": chat.is_saved,
             "archived": archived,
+            "pinned": pinned,
             "unread_count": unread_count,
             "pinned_message_id": chat.pinned_message_id,
             "members_count": members_count,
@@ -501,3 +503,17 @@ async def set_chat_archived_for_user(
     await db.commit()
     await db.refresh(chat)
     return chat
+
+
+async def set_chat_pinned_for_user(
+    db: AsyncSession,
+    *,
+    chat_id: int,
+    user_id: int,
+    pinned: bool,
+) -> Chat:
+    chat, _membership = await _get_chat_and_membership(db, chat_id=chat_id, user_id=user_id)
+    await repository.upsert_chat_pinned_setting(db, chat_id=chat_id, user_id=user_id, pinned=pinned)
+    await db.commit()
+    await db.refresh(chat)
+    return chat