Allow artists to manage their own albums / profile etc

[chrislo]

At the moment the admin interface for creating artists and editing albums is restricted to signed in users. To reduce the work and empower the artists we want to allow them to manage their own albums, add and publish new ones etc.

To begin with we probably still want to manually add new user accounts (rather than have a free-for-all sign up) so some kind of invitation flow is needed. The edit options need to be scoped to those users (so an artist can manage their own releases but not those of other artists).

• Invite someone to create a user account
• Associate invitations with existing artists
• Allow them to add new albums
• Allow them to edit existing albums
• Allow them to edit artist profile
• Prevent artists from editing anything except their own album and artist pages