Rewrite function that builds form data for app environment roles form.

- Adds a property to ApplicationRole model so that it knows its related
  EnvironmentRole models.
- Rewrite the form data builder in the routes file so that it loops the
  application members and their environment roles to build the data
  structure.

tests/models/test_application_role.py

@@ -1,7 +1,7 @@
 from atst.domain.permission_sets import PermissionSets
 from atst.models.audit_event import AuditEvent
 
-from tests.factories import PortfolioFactory, UserFactory
+from tests.factories import *
 
 
 def test_has_application_role_history(session):
@@ -38,3 +38,13 @@ def test_has_application_role_history(session):
     old_state, new_state = changed_event.changed_state["permission_sets"]
     assert old_state == [PermissionSets.VIEW_APPLICATION]
     assert new_state == [PermissionSets.EDIT_APPLICATION_TEAM]
+
+
+def test_environment_roles():
+    application = ApplicationFactory.create()
+    environment = EnvironmentFactory.create(application=application)
+    user = UserFactory.create()
+    application_role = ApplicationRoleFactory.create(application=application, user=user)
+    environment_role = EnvironmentRoleFactory.create(environment=environment, user=user)
+
+    assert application_role.environment_roles == [environment_role]