Remove computed SMS prefix

This is no longer used no that the column in the table (`prefix_sms`) is
populated.

app/delivery/send_to_providers.py

@@ -48,13 +48,11 @@ def send_sms_to_provider(notification):
         )
         template_model = dao_get_template_by_id(notification.template_id, notification.template_version)
 
-        sender_has_been_customised = (not service.get_prefix_sms_with_service_name())
-
         template = SMSMessageTemplate(
             template_model.__dict__,
             values=notification.personalisation,
             prefix=service.name,
-            sender=sender_has_been_customised,
+            show_prefix=service.prefix_sms,
         )
 
         if service.research_mode or notification.key_type == KEY_TYPE_TEST:

app/models.py

@@ -283,11 +283,6 @@ class Service(db.Model, Versioned):
         default_letter_contact = [x for x in self.letter_contacts if x.is_default]
         return default_letter_contact[0].contact_block if default_letter_contact else None
 
-    def get_prefix_sms_with_service_name(self):
-        if self.prefix_sms is not None:
-            return self.prefix_sms
-        return self.get_default_sms_sender() == current_app.config['FROM_NUMBER']
-
 
 class AnnualBilling(db.Model):
     __tablename__ = "annual_billing"

app/schemas.py

@@ -209,7 +209,6 @@ class ServiceSchema(BaseSchema):
     reply_to_email_address = fields.Method(method_name="get_reply_to_email_address")
     sms_sender = fields.Method(method_name="get_sms_sender")
     letter_contact_block = fields.Method(method_name="get_letter_contact")
-    prefix_sms_with_service_name = fields.Method(method_name="get_prefix_sms_with_service_name")
 
     def service_permissions(self, service):
         return [p.permission for p in service.permissions]
@@ -223,9 +222,6 @@ class ServiceSchema(BaseSchema):
     def get_letter_contact(self, service):
         return service.get_default_letter_contact()
 
-    def get_prefix_sms_with_service_name(self, service):
-        return service.get_prefix_sms_with_service_name()
-
     class Meta:
         model = models.Service
         dump_only = ['reply_to_email_address', 'letter_contact_block']

tests/app/service/test_rest.py

@@ -158,7 +158,6 @@ def test_get_service_by_id(client, sample_service):
     assert json_resp['data']['branding'] == 'govuk'
     assert json_resp['data']['dvla_organisation'] == '001'
     assert json_resp['data']['sms_sender'] == current_app.config['FROM_NUMBER']
-    assert json_resp['data']['prefix_sms_with_service_name'] is True
     assert json_resp['data']['prefix_sms'] is True
 
 
@@ -1546,7 +1545,7 @@ def test_prefixing_messages_based_on_prefix_sms(
         headers=[('Content-Type', 'application/json'), create_authorization_header()]
     )
     service = json.loads(result.get_data(as_text=True))['data']
-    assert service['prefix_sms_with_service_name'] == should_prefix
+    assert service['prefix_sms'] == should_prefix
 
 
 @pytest.mark.parametrize('posted_value, stored_value, returned_value', [
@@ -1567,10 +1566,6 @@ def test_set_sms_prefixing_for_service(
         _data={'prefix_sms': posted_value},
     )
     assert result['data']['prefix_sms'] == stored_value
-    # This derived value will go away eventually, once we’ve done a migration
-    assert result['data']['prefix_sms_with_service_name'] == returned_value
-    # The derived value is dependent on the service sending from the platform’s
-    # default from number
     assert result['data']['sms_sender'] == current_app.config['FROM_NUMBER']