- `ChatChannel`
- `UserChatChannelMembership`
Also creates a new `chat-direct-message` model used as the object for the`chatable` property of the `ChatChannel` when the `ChatChannel` is a direct message channel. When the chatable is a category a real `Category` object will now be returned.
Archive state of a `ChatChannel` is now hold in a `ChatChannelArchive` object.
1. `test()` and `render()` instead of `componentTest()`
2. Angle brackets
3. `strictEqual()`/`true()`/`false()` assertions
This removes all remaining uses of `componentTest` from core
This is a followup of the previous refactor where we created two new
models to handle all the dedicated logic that was present in the
`ChatChannel` model.
For the sake of consistency, `DMChannel` has been renamed to
`DirectMessageChannel` and the previous `DirectMessageChannel` model is
now named `DirectMessage`. This should help reasoning about direct
messages.
