Remove dependence on domains.yml from settings

Settings looked at `domains.yml` when users were making go live requests
or email branding requests.

This will allow us to remove the `domains.yml` file, by using
information about organisations that is now stored in the database
instead.

app/models/organisation.py

@@ -31,13 +31,12 @@ class Organisation(JSONModel):
     def crown_status(self):
         return self.crown
 
-    @property
-    def as_human_readable(self):
+    def as_human_readable(self, fallback_domain):
         if 'dwp.' in ''.join(self.domains):
             return 'DWP - Requires OED approval'
         if self.agreement_signed:
             return 'Yes, on behalf of {}'.format(self.name)
-        elif self.owner:
+        elif self.name:
             return '{} (organisation is {}, {})'.format(
                 {
                     False: 'No',
@@ -51,11 +50,10 @@ class Organisation(JSONModel):
                 }.get(self.crown_status),
             )
         else:
-            return 'Can’t tell (domain is {})'.format(self._domain)
+            return 'Can’t tell (domain is {})'.format(fallback_domain)
 
-    @property
-    def as_info_for_branding_request(self):
-        return self.owner or 'Can’t tell (domain is {})'.format(self._domain)
+    def as_info_for_branding_request(self, fallback_domain):
+        return self.name or 'Can’t tell (domain is {})'.format(fallback_domain)
 
     @property
     def as_jinja_template(self):

app/models/service.py

@@ -396,10 +396,6 @@ class Service(JSONModel):
             organisations_client.get_service_organisation(self.id)
         )
 
-    @property
-    def organisation_name(self):
-        return self.organisation.name
-
     @cached_property
     def inbound_number(self):
         return inbound_number_client.get_inbound_sms_number_for_service(self.id)['data'].get('number', '')