Fix setting of broadcast permission

This was broken because current_service doesn’t update itself after
calling the `update` method of the API. So we thought we were changing
the permissions like this:
```
{'email', 'sms', 'letter'}
{'email', 'sms', 'letter', 'broadcast'}
{'sms', 'letter', 'broadcast'}
{'letter', 'broadcast'}
{'broadcast'}
```

But actually we were doing this:
```
{'email', 'sms', 'letter'}
{'email', 'sms', 'letter', 'broadcast'}
{'sms', 'letter'}
{'email', 'letter'}
{'email', 'sms'}
```

This commit changes the code to update the permissions like this:
```
{'email', 'sms', 'letter'}
{'broadcast'}
```

It does so by adding a new method to the service model which changes all
the permissions in one API call, and updates the tests to mock the
underlying API call, not the method on the model.

app/main/views/service_settings.py

@@ -318,10 +318,7 @@ def service_set_broadcast_permission(service_id):
     if form.validate_on_submit():
 
         if form.enabled.data:
-            current_service.force_permission('broadcast', on=True)
-            current_service.force_permission('email', on=False)
-            current_service.force_permission('sms', on=False)
-            current_service.force_permission('letter', on=False)
+            current_service.force_broadcast_permission_on()
         else:
             current_service.force_permission('broadcast', on=False)
 

app/models/service.py

@@ -99,6 +99,11 @@ class Service(JSONModel):
             permissions | permission if on else permissions - permission,
         )
 
+    def force_broadcast_permission_on(self):
+        return self.update_permissions(
+            set(self.permissions) - {'email', 'sms', 'letter'} | {'broadcast'}
+        )
+
     def update_permissions(self, permissions):
         return self.update(permissions=list(permissions))
 

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

@@ -1,5 +1,4 @@
 import functools
-from unittest.mock import call
 
 import pytest
 from flask import url_for
@@ -39,34 +38,55 @@ def test_service_set_permission_requires_platform_admin(
     )
 
 
-@pytest.mark.parametrize('permission, form_data, expected_calls', [
-    ('inbound_sms', 'True', [
-        call('inbound_sms', on=True),
-    ]),
-    ('inbound_sms', 'False', [
-        call('inbound_sms', on=False),
-    ]),
-    ('email_auth', 'True', [
-        call('email_auth', on=True),
-    ]),
-    ('email_auth', 'False', [
-        call('email_auth', on=False),
-    ]),
-    ('international_letters', 'True', [
-        call('international_letters', on=True),
-    ]),
-    ('international_letters', 'False', [
-        call('international_letters', on=False),
-    ]),
-    ('broadcast', 'True', [
-        call('broadcast', on=True),
-        call('email', on=False),
-        call('sms', on=False),
-        call('letter', on=False),
-    ]),
-    ('broadcast', 'False', [
-        call('broadcast', on=False),
-    ]),
+@pytest.mark.parametrize('initial_permissions, permission, form_data, expected_update', [
+    (
+        [],
+        'inbound_sms',
+        'True',
+        ['inbound_sms'],
+    ),
+    (
+        ['inbound_sms'],
+        'inbound_sms',
+        'False',
+        [],
+    ),
+    (
+        [],
+        'email_auth',
+        'True',
+        ['email_auth'],
+    ),
+    (
+        ['email_auth'],
+        'email_auth',
+        'False',
+        [],
+    ),
+    (
+        [],
+        'international_letters',
+        'True',
+        ['international_letters'],
+    ),
+    (
+        ['international_letters'],
+        'international_letters',
+        'False',
+        [],
+    ),
+    (
+        ['email', 'sms', 'letter', 'international_sms', 'international_letters'],
+        'broadcast',
+        'True',
+        ['international_sms', 'international_letters', 'broadcast'],
+    ),
+    (
+        ['broadcast', 'international_sms', 'international_letters'],
+        'broadcast',
+        'False',
+        ['international_sms', 'international_letters'],
+    ),
 ])
 def test_service_set_permission(
     mocker,
@@ -74,17 +94,23 @@ def test_service_set_permission(
     service_one,
     mock_get_inbound_number_for_service,
     permission,
+    initial_permissions,
     form_data,
-    expected_calls,
+    expected_update,
 ):
-    force_permission = mocker.patch('app.models.service.Service.force_permission')
+    service_one['permissions'] = initial_permissions
+    mock_update_service = mocker.patch('app.service_api_client.update_service')
     response = platform_admin_client.post(
         url_for('main.service_set_permission', service_id=service_one['id'], permission=permission),
         data={'enabled': form_data}
     )
     assert response.status_code == 302
     assert response.location == url_for('main.service_settings', service_id=service_one['id'], _external=True)
-    assert force_permission.call_args_list == expected_calls
+
+    assert mock_update_service.call_args[0][0] == service_one['id']
+    new_permissions = mock_update_service.call_args[1]['permissions']
+    assert len(new_permissions) == len(set(new_permissions))
+    assert set(new_permissions) == set(expected_update)
 
 
 @pytest.mark.parametrize('service_fields, endpoint, kwargs, text', [