Assign email branding based on user’s email domain

When a user creates a service we can take a pretty good guess at what
organisation they’re from.

For many organisations, especially local councils, GOV.UK branding is
not appropriate for their service. But right now every service:
- gets created with GOV.UK branding
- has to ask us to change it, even if they’ve already done so for other
  services they run

This commit starts using the `domain` field on the email branding table
to lookup what email branding to assign to a service automatically,
where we’re sure there’s a sensible default.

app/main/views/add_service.py

@@ -5,6 +5,7 @@ from werkzeug.exceptions import abort
 
 from app import (
     billing_api_client,
+    email_branding_client,
     invite_api_client,
     service_api_client,
     user_api_client,
@@ -12,7 +13,7 @@ from app import (
 from app.main import main
 from app.main.forms import CreateServiceForm
 from app.notify_client.models import InvitedUser
-from app.utils import email_safe, is_gov_user
+from app.utils import AgreementInfo, email_safe, is_gov_user
 
 
 def _add_invited_user_to_service(invited_user):
@@ -27,6 +28,9 @@ def _add_invited_user_to_service(invited_user):
 
 def _create_service(service_name, organisation_type, email_from, form):
     free_sms_fragment_limit = current_app.config['DEFAULT_FREE_SMS_FRAGMENT_LIMITS'].get(organisation_type)
+    email_branding = email_branding_client.get_email_branding_id_for_domain(
+        AgreementInfo.from_current_user().canonical_domain
+    )
     try:
         service_id = service_api_client.create_service(
             service_name=service_name,
@@ -38,6 +42,9 @@ def _create_service(service_name, organisation_type, email_from, form):
         )
         session['service_id'] = service_id
 
+        if email_branding:
+            service_api_client.update_service(service_id, email_branding=email_branding)
+
         billing_api_client.create_or_update_free_sms_fragment_limit(service_id, free_sms_fragment_limit)
 
         return service_id, None