Add test_app model that is visible to all users but has permissions for CUD (and test it)

[AlanCoding]

Filing after reading comment:

ansible/galaxy_ng#2162 (comment)

This scenario seems perfectly coherent, and it should be perfectly compatible with DAB RBAC.

• all records of a particular model are visible to all users in the system
• only users who are specifically granted permission to modify that model can make changes - CUD - Create Update and Delete

I expect we have a few cases where DAB RBAC assumed that a model has a "view" permission. We need docs to set expectations about configuration of this. For example, if the Meta doesn't list "view" permission is that enough to assume that all users can view all entries? If so, that probably needs a special case in the logic going into access_qs and stuff. So there's at least 1 thing to do.

Also need to test that custom roles and role_metadata work as expected.