Make SMS sender dependent on estimated SMS volumes

We have a number of go live requests where people have said they’re
sending text messages, but haven’t changed the text message sender from
the default of `GOVUK` (we ask teams who aren’t central government to do
this). At the moment we don’t prompt them to, because we look at whether
they have text message templates as indicative of whether they’re going
to send text messages.

Now that we explicitly ask for the volumes of text messages they’re
sending we should use this to determine whether or not we prompt them to
change their text message sender because it’s a stronger signal of
intent than what templates they’ve set up.

app/models/service.py

@@ -269,7 +269,7 @@ class Service():
     @property
     def needs_to_change_sms_sender(self):
         return all((
-            self.has_sms_templates,
+            self.volume_sms,
             self.shouldnt_use_govuk_as_sms_sender,
             self.sms_sender_is_govuk,
         ))

tests/app/main/views/test_service_settings.py

@@ -1176,7 +1176,7 @@ def test_should_redirect_after_request_to_go_live(
             False,
             True,
             True,
-            1, 1, 1,
+            1, 0, 1,
             'No',
             True,
             [
@@ -1228,7 +1228,7 @@ def test_should_redirect_after_request_to_go_live(
             True,
             True,
             False,
-            1, 1, 1,
+            1, 0, 0,
             'No',
             True,
             [
@@ -1275,7 +1275,6 @@ def test_should_redirect_after_request_to_go_live(
                 'notify_request_to_go_live_incomplete_mou',
                 'notify_request_to_go_live_incomplete_team_member',
                 'notify_request_to_go_live_incomplete_template_content',
-                'notify_request_to_go_live_incomplete_sms_sender',
             ],
         ),
     ),