Edit User Profile: Role dropdown

[ErisDS]

In the template for the user edit screen, there is a commented out role dropdown:
https://github.com/TryGhost/Ghost/blob/master/core/client/templates/settings/users/user.hbs#L67

We now have the Roles API browse endpoint for fetching the roles that the currently logged in user is allowed to assign (although it won't function 100% until #3395 is merged)

We also have the User API edit endpoint updated to expect to have to change a role, and to check permissions for what roles can be assigned.

Therefore, all the pieces should be in place to wire this up. The dropdown needs uncommenting, populating with a list, and hiding if the list is empty.

You can reference #3083 to see who should be allowed to assign a given role, but in short:

• Owners & Admins can assign all roles, except the 'Owner' role won't appear in the list, that role can only be assigned via the 'Make owner' button User settings cog menu (show items appropriate to role) #3400.
• Editors can assign the author role.
• Authors are not allowed to assign any roles, so this dropdown should be empty, and therefore should be hidden for authors.

Update: This dropdown shouldn't appear when editing the current logged in user's profile, i.e. it shouldn't be possible to edit your own role as it's a pretty destructive action & too easy to do. Authors can't edit roles, owners can't relinquish their ownership without doing the explicit "Transfer ownership" action, so only admins and editors are affected, and they are only prevented from downgrading themselves which seems like a minimal use-case anyway.

[novaugust]

I'd love to take this over the weekend, been too long since I got to do some ghosting :)

[novaugust]

For editors, being able to assign the author role is as good as being unable to assign a role, no?

[JohnONolan]

Good point - probably doesn't make sense for editors to be able to see the role dropdown (on the edit-user screen)