Start to remove use of the term "roles"

We don't use this term consistently and it's not defined anywhere.
Since most of the Admin app deals with user-facing permssions, it's
OK to just use the term "permissions". Where both types of permission
are present in the same file, we can more clearly distinguish them
as "UI permissions" and "DB permissions".

app/models/user.py

@@ -17,7 +17,7 @@ from app.notify_client.org_invite_api_client import org_invite_api_client
 from app.notify_client.user_api_client import user_api_client
 from app.utils.user import is_gov_user
 from app.utils.user_permissions import (
-    all_permissions,
+    all_ui_permissions,
     translate_permissions_from_db_to_admin_roles,
 )
 
@@ -201,7 +201,7 @@ class User(JSONModel, UserMixin):
         return self._platform_admin and not session.get('disable_platform_admin_view', False)
 
     def has_permissions(self, *permissions, restrict_admin_usage=False, allow_org_user=False):
-        unknown_permissions = set(permissions) - all_permissions
+        unknown_permissions = set(permissions) - all_ui_permissions
         if unknown_permissions:
             raise TypeError('{} are not valid permissions'.format(list(unknown_permissions)))