Refactor organisation branding into model

This is the same way we handle lazy-loading the branding in the service
model.

app/main/views/organisations.py

@@ -222,25 +222,8 @@ def cancel_invited_org_user(org_id, invited_user_id):
 @main.route("/organisations/<org_id>/settings/", methods=['GET'])
 @user_is_platform_admin
 def organisation_settings(org_id):
-
-    email_branding = 'GOV.UK'
-
-    if current_organisation.email_branding_id:
-        email_branding = email_branding_client.get_email_branding(
-            current_organisation.email_branding_id
-        )['email_branding']['name']
-
-    letter_branding = None
-
-    if current_organisation.letter_branding_id:
-        letter_branding = letter_branding_client.get_letter_branding(
-            current_organisation.letter_branding_id
-        )['name']
-
     return render_template(
         'views/organisations/organisation/settings/index.html',
-        email_branding=email_branding,
-        letter_branding=letter_branding,
     )
 
 

app/models/organisation.py

@@ -2,6 +2,8 @@ from flask import abort
 from werkzeug.utils import cached_property
 
 from app.models import JSONModel, ModelList
+from app.notify_client.email_branding_client import email_branding_client
+from app.notify_client.letter_branding_client import letter_branding_client
 from app.notify_client.organisations_api_client import organisations_client
 
 
@@ -148,6 +150,26 @@ class Organisation(JSONModel):
             key=lambda user: user.email_address.lower(),
         )
 
+    @cached_property
+    def email_branding(self):
+        if self.email_branding_id:
+            return email_branding_client.get_email_branding(
+                self.email_branding_id
+            )['email_branding']
+
+    @property
+    def email_branding_name(self):
+        if self.email_branding_id:
+            return self.email_branding['name']
+        return 'GOV.UK'
+
+    @cached_property
+    def letter_branding(self):
+        if self.letter_branding_id:
+            return letter_branding_client.get_letter_branding(
+                self.letter_branding_id
+            )
+
     def update(self, **kwargs):
         response = organisations_client.update_organisation(self.id, **kwargs)
         self.__init__(response)

app/templates/views/organisations/organisation/settings/index.html

@@ -73,7 +73,7 @@
       {% endcall %}
       {% call row() %}
         {{ text_field('Default email branding') }}
-        {{ text_field(email_branding) }}
+        {{ text_field(current_org.email_branding_name) }}
         {{ edit_field(
             'Change',
             url_for('.edit_organisation_email_branding', org_id=current_org.id)
@@ -83,7 +83,7 @@
       {% call row() %}
         {{ text_field('Default letter branding') }}
         {{ optional_text_field(
-          letter_branding,
+          current_org.letter_branding.name,
           default='No branding'
         ) }}
         {{ edit_field(