channels: turn MessageStore into trait

[jondot]

Then supply:

• InMemoryMessageStore: inprocess/current process persistence of messages
• DBMessageStore: hooks into our DB implementation, also provides table migrations, through a generator

Notes:

• In both cases we should strive for most of the logic to turn into a generic logic that appears in the framework, and then some "glue" that appears in code that is generated.
• Once we use a MessageStore trait, we can now provide event handlers as well, by chat models. Because we set up the trait in app.rs this can seamlessly persist data to DB, and the user configures almost nothing to get a fully functioning chat.
  • SingleRoomChatModel - join leaves all channels, then joins a selected room, message appends a message
  • MultiRoomChatModel - join joins a new room, message selects which room to append to, leave leaves a room

[kaplanelad]

see