Overfetching data

In [room-resolver.ts](https://github.com/anuraghazra/convoychat/blob/8eedf6d67d4502ed9cc43ccfbcd25d222bf8e5d6/server/modules/room/room-resolver.ts)

- [ ] **Overfetching rooms**
We have two queries `listRooms` and `listCurrentUserRooms`.
When you execute both queries on the client side, we run into a situation where room data is over fetched.

- [ ] **Overfetching message author**
There is a possibility that a user can be a part of multiple rooms and many messages can have the same users.
You can fix this by using field resolver with dataloader.

The second one is a must I think.