add broadcast service permission

tests/app/main/views/service_settings/test_service_setting_permissions.py

@@ -45,6 +45,8 @@ def test_service_set_permission_requires_platform_admin(
     ('email_auth', 'False', False),
     ('international_letters', 'True', True),
     ('international_letters', 'False', False),
+    ('broadcast', 'True', True),
+    ('broadcast', 'False', False),
 ])
 def test_service_set_permission(
     mocker,

tests/app/main/views/test_service_settings.py

@@ -107,6 +107,7 @@ def mock_get_service_settings_page_common(
         'Data retention email Change',
         'Receive inbound SMS Off Change',
         'Email authentication Off Change',
+        'Send cell broadcasts Off Change',
     ]),
 ])
 def test_should_show_overview(