cleanup, add test for workspace user permissions

atst/models/workspace_user.py

@@ -9,13 +9,6 @@ class WorkspaceUser(object):
         self.user = user
         self.workspace_role = workspace_role
 
-    def permissions(self):
-        atat_permissions = set(self.user.atat_role.permissions)
-        workspace_permissions = (
-            [] if self.workspace_role is None else self.workspace_role.role.permissions
-        )
-        return set(workspace_permissions).union(atat_permissions)
-
     @property
     def workspace(self):
         return self.workspace_role.workspace