Tell people to change their branding

In some cases it’s not appropriate for teams to have GOV.UK branding.
But they all start with it by default, if we can’t make a better guess.
We should be more explicit about this to reduce the number of teams
sending emails with the wrong branding.

app/models/service.py

@@ -417,6 +417,10 @@ class Service(JSONModel):
             return 'GOV.UK'
         return self.email_branding['name']
 
+    @property
+    def needs_to_change_email_branding(self):
+        return self.email_branding_id is None and self.organisation_type != 'central'
+
     @property
     def letter_branding_id(self):
         return self._dict['letter_branding']

app/templates/views/service-settings/branding/email-options.html

@@ -17,10 +17,16 @@
     back_link=url_for('main.service_settings', service_id=current_service.id)
   ) }}
 
-  <p class="form-group">
+  <p>
     Your emails currently have {{ current_service.email_branding_name }} branding.
   </p>
 
+  {% if current_service.needs_to_change_email_branding %}
+    <p>
+      You should be using your own branding instead. We can help you to set this up.
+    </p>
+  {% endif %}
+
   {% call form_wrapper() %}
     {% if form.something_else_is_only_option %}
       {{ textbox(