Initial migration and changes to models as well as
changing the following services to update last_message_id:
* Chat::MessageCreator
* Chat::RestoreMessage
* Chat::TrashMessage
The data migration will set the `last_message_id` for all existing
threads and channels in the database.
When we query the thread list as well as the channel,
we look at the last message ID for the following:
* Channel - Sorting DM channels, and channel metadata for the list of channels
* Thread - Last reply details for thread indicators and thread list
