* convert statuses.visibility and notifications.notification_type columns from type string -> int for performance / space savings
* fix test trying to compare string to int
* fix instance count query using string literal instead of gtsmodel const type
* ensure a default value is always set
* also migrate the account settings and sin bin status tables
* initialize maps outside loops and place into singular enum mapping creation func
* use int16 for enum types
* update sinbinstatus creation to be from a snapshot at initial creation
* add snapshot of poll type at creation time
This adds the preferences endpoint to our Mastodon Client API
implementation. It's a read-only endpoint that returns a number of
user preferences. Applications can query these settings when logging in
a user (for the first time) to configure themselves.