This commit will now allow us to track read position in a thread and returns to this position when you open the thread.
Note this commit is also extracting the following components to make it possible:
- `<ChatMessagesScroller />`
- `<ChatMessagesContainer />`
The `UpdateUserThreadLastRead` has been updated to allow this.
Various refactorings have also been done to the code and specs to improve the support of last read.
52e8d57293