Add a page to set organisation and branding option

Platform admin only.

Adds radio buttons to choose one of:
- three hard-coded branding options
- organisations from a list provided by the API

app/templates/views/service-settings.html

@@ -18,6 +18,10 @@
         'title': 'Set email reply to address',
         'link': url_for('.service_set_reply_to_email', service_id=current_service.id)
       },
+      {
+        'title': 'Set email branding',
+        'link': url_for('.service_set_branding_and_org', service_id=current_service.id)
+      } if current_user.has_permissions([], admin_override=True) else {},
       {
         'title': 'Set text message sender name',
         'link': url_for('.service_set_sms_sender', service_id=current_service.id)
@@ -51,7 +55,7 @@
         'title': 'Take service out of research mode',
         'link': url_for('.service_switch_research_mode', service_id=current_service.id)
       } if current_service.research_mode and current_user.has_permissions([], admin_override=True) else {
-      },
+      }
     ]) }}
 
 {% endblock %}

app/templates/views/service-settings/set-branding-and-org.html

@@ -0,0 +1,25 @@
+{% extends "withnav_template.html" %}
+{% from "components/radios.html" import radios, branding_radios %}
+{% from "components/page-footer.html" import page_footer %}
+
+{% block page_title %}
+  Set branding and organisation – GOV.UK Notify
+{% endblock %}
+
+{% block maincolumn_content %}
+
+  <h1 class="heading-large">Set email branding</h1>
+  <div class="grid-row">
+    <div class="column-three-quarters">
+      <form method="post">
+        {{ radios(form.branding_type) }}
+        {{ branding_radios(form.organisation, branding_dict=branding_dict) }}
+        {{ page_footer(
+          'Save',
+          back_link=url_for('.service_settings', service_id=current_service.id)
+        ) }}
+      </form>
+    </div>
+  </div>
+
+{% endblock %}