1:1 chats export v0

[ryanfkeepers]

Exports take a RestoreCollection and creates ExportCollections out of it after transforming the data into a format that can be consumable by an end user (like files for drive items or ics for calendar events).

• Convert individual items from raw backup data to raw json

Chats should be able to re-use channel message export design, since the message entity format is nearly identical.