There was a bug in the application settings route that threw an error if
an environment role and its associated application role did not have an
associated user. Updated to check for the user name on the application role.
In the future, an `application_invitation1 will not refer to a `user` until
someone accepts the invitation; they'll only reference an
`application_role`. When a user is invited to an application, the
inviter can specify the environments the invitee should have access to.
For this to be possible, an `environment_role` should reference an
`application_role`, because no `user` entity will be known at that time.
In addition to updating all the models and domain methods necessary for
this change, this commit deletes unused code and tests that were
dependent on `environment_roles` having a `user_id` foreign key.
Use ApplicationRole.id instead of User.id in forms. This eliminates the
need for the function that checks whether a user is in a given
application, because looking up the application role will raise an error
if the user is not.
- uses two route functions - one for update app, another for add
environment
- uses a second form for the app settings page
- uses the /environments/new url naming convention
