Model for OSF APIv2 registrations. This model may be used with one of several API endpoints. It may be queried directly, or accessed via relationship fields. For field and usage information, see:

• https://api.osf.io/v2/docs/#!/v2/Registration_List_GET
• https://api.osf.io/v2/docs/#!/v2/Registration_Detail_GET
• https://api.osf.io/v2/docs/#!/v2/Registration_Children_List_GET
• https://api.osf.io/v2/docs/#!/v2/User_Registrations_GET