Use application_role_id on environment_roles.

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.

tests/routes/applications/test_init.py

@@ -1,33 +1,16 @@
 from flask import url_for, get_flashed_messages
 
-from tests.factories import (
-    UserFactory,
-    PortfolioFactory,
-    PortfolioRoleFactory,
-    EnvironmentRoleFactory,
-    EnvironmentFactory,
-    ApplicationFactory,
-)
-
-from atst.domain.applications import Applications
-from atst.domain.portfolios import Portfolios
-from atst.models.portfolio_role import Status as PortfolioRoleStatus
-
-from tests.utils import captured_templates
-
-
-def create_environment(user):
-    portfolio = PortfolioFactory.create()
-    portfolio_role = PortfolioRoleFactory.create(portfolio=portfolio, user=user)
-    application = ApplicationFactory.create(portfolio=portfolio)
-    return EnvironmentFactory.create(application=application, name="new environment!")
+from tests.factories import *
 
 
 def test_environment_access_with_env_role(client, user_session):
     user = UserFactory.create()
-    environment = create_environment(user)
-    env_role = EnvironmentRoleFactory.create(
-        user=user, environment=environment, role="developer"
+    environment = EnvironmentFactory.create()
+    app_role = ApplicationRoleFactory.create(
+        user=user, application=environment.application
+    )
+    EnvironmentRoleFactory.create(
+        application_role=app_role, environment=environment, role="developer"
     )
     user_session(user)
     response = client.get(
@@ -39,7 +22,7 @@ def test_environment_access_with_env_role(client, user_session):
 
 def test_environment_access_with_no_role(client, user_session):
     user = UserFactory.create()
-    environment = create_environment(user)
+    environment = EnvironmentFactory.create()
     user_session(user)
     response = client.get(
         url_for("applications.access_environment", environment_id=environment.id)