Summary:
- Allows nulls for a number of fields meaning largely empty drafts can
be stored.
- Adds 'uniqueid', an id unique to each issuer which is intended
to be used as a parameter in both the initiate login and dynamic
registration urls provided to platforms, as a means to identify specific
registrations for the issuer, in the absense of client_id (optional in
the 1.3 spec).
- Add 'status', used to denote draft or active registrations.