Remove dependence on domains.yml from static pages

This will allow us to remove the `domains.yml` file, by using
information about organisations that is now stored in the database
instead.

tests/conftest.py

@@ -3125,6 +3125,27 @@ def mock_get_organisation(
     return mocker.patch('app.organisations_client.get_organisation', side_effect=_get_organisation)
 
 
+@pytest.fixture(scope='function')
+def mock_get_organisation_by_domain(
+    mocker,
+    name=False,
+    crown=True,
+    agreement_signed=False,
+):
+    def _get_organisation_by_domain(org_id):
+        return organisation_json(
+            org_id,
+            name,
+            crown=crown,
+            agreement_signed=agreement_signed,
+        )
+
+    return mocker.patch(
+        'app.organisations_client.get_organisation_by_domain',
+        side_effect=_get_organisation_by_domain,
+    )
+
+
 @pytest.fixture(scope='function')
 def mock_get_service_organisation(mocker):
     def _get_service_organisation(service_id):