Application users should have access to portfolio landing page.

- Adds override to portfolio landing page access check to see if user
  has access to any applications within the portfolio.
- Route for accepting an application invitation redirects directly to
  portfolio applications route.
- Tests ensure application user only sees apps the user has access to on
  the portfolio landing page.

tests/routes/applications/test_invitations.py

@@ -16,8 +16,26 @@ def test_accept_application_invitation(client, user_session):
 
     assert response.status_code == 302
     expected_location = url_for(
-        "portfolios.show_portfolio",
+        "applications.portfolio_applications",
         portfolio_id=application.portfolio_id,
         _external=True,
     )
     assert response.location == expected_location
+
+
+def test_accept_application_invitation_end_to_end(client, user_session):
+    user = UserFactory.create()
+    application = ApplicationFactory.create(name="Millenium Falcon")
+    app_role = ApplicationRoleFactory.create(application=application, user=user)
+    invite = ApplicationInvitationFactory.create(
+        role=app_role, user=user, inviter=application.portfolio.owner
+    )
+
+    user_session(user)
+    response = client.get(
+        url_for("applications.accept_invitation", token=invite.token),
+        follow_redirects=True,
+    )
+
+    assert response.status_code == 200
+    assert application.name in response.data.decode()