This commit adds new tables to the database and APIs in `Messenger` and
communities `Manager` to store `CheckChannelPermissionsResponse`s.
The responses are stored whenever channel permissions have been checked.
The reason we're doing this is so that clients can retrieve the last
known channel permission state before waiting for onchain checks to
finish.
We only write up migrations, down migrations are not always possible in sqlite or
too complex/too expensive. For example to remove a column you would have to duplicate
the table, copy over the data, delete and recreated.
This can be very expensive for some tables (user_messages for example), so should not be attempted.
Notes
One issue we faced multiple times is that updates to user_messages can be very
expensive, leading to slow upgrade times and interrupted migrations. So avoid
writes if not necessary.
b8b402da8d