Enable testing for gregui

Remove the 'email' and 'mobile_phone' fields on Person and use identities to represent this data instead.

- Migrate data on existing Person objects to Identity objects
- Make the 'is verified' logic only accept certain ID types
- Sync the Person.is_verified and API 'verified' filter logic

Issue: GREG-66

Isuse: GREG-66

Before this commit, the userinfo endpoint would fail if the user
did not have a person object connected to their GregUserProfile. We now
check that this is the case before checking the person objects roles.

- Introduces the Invitation and InvitationLink models for keeping track
  of guest invitations and the links connected to them.
- Adds a post endpoint accessible by sponsors to create invitations for
  guests.
- Adds a get endpoint for the guests to review their invitation
  information.
- Adds a post endpoint for the guests to confirm their invitation with
  updated mobile_phone number if they want.
- Removes token field from Person since it is not used.

Issue: GREG-42

Issue: GREG-42

Issue: GREG-42

Issue: GREG-42

Issue: GREG-42

Register page now fetches OUs the sponsor has access to.
Sponsor page now shows the sponsor's active and waiting guests.

Resolves: GREG-63

Issue: GREG-36

Issue: GREG-36

Issue: GREG-36

Issue: GREG-36

Issue: GREG-36

person/sponsor

Issue: GREG-36

Issue: GREG-35