Schema proposals for MVP

[PPartisan]

For our first release, our backend needs to support the following features:

• An admin must be able to create accounts manually.
• A user must be able to log in with credentials supplied by an admin.
• Users must be able to join a single chatroom.
• Users must be able to post messages in the chatroom, and the new message must be broadcast to all other chatroom participants in real-time.
• There must be a character limit on the maximum message size.
  Users must be able to request a new username through the Roky app. If the username is available, it will be assigned to them. It will not be assigned to them if it is unavailable or uses illegal characters.

Here is a link to our proposed schema: DrawSQL.

Please propose amendments as comments and a rationale for the proposed change.