Add page where users can say they want branding

At the moment branding is an undocumented feature. We get a bunch of
support tickets from teams asking its possible.

This commit:
- lets people know it’s possible, and what the options are
- is the first step towards making this process as self-service as
  possible

In some cases we will be able to infer a user’s organisation from there
email address, and Google image search their logo. So the experience for
them is that they press a button and government just sorts it out for
you (also known as "the dream").

In other cases we will have to get back to people asking for a copy of
their logo, or to find out about their service, but this is what we have
to do at the moment anyway.

app/templates/views/service-settings.html

@@ -89,6 +89,17 @@
             }}
           {% endcall %}
 
+          {% call row() %}
+            {{ text_field('Email branding') }}
+            {{ text_field(
+              'GOV.UK' if current_service.branding == 'govuk' else 'Your branding'
+            ) }}
+            {{ edit_field(
+              'Change',
+              url_for('.branding_request', service_id=current_service.id),
+            )}}
+          {% endcall %}
+
         {% endif %}
 
       {% endcall %}

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

@@ -0,0 +1,46 @@
+{% extends "withnav_template.html" %}
+{% from "components/radios.html" import radio %}
+{% from "components/textbox.html" import textbox %}
+{% from "components/page-footer.html" import page_footer %}
+
+{% block service_page_title %}
+  Email branding
+{% endblock %}
+
+{% block maincolumn_content %}
+
+  <h1 class="heading-large">Email branding</h1>
+
+  <form method="post">
+    <fieldset class="form-group {% if form.options.errors %}form-group-error{% endif %} top-gutter">
+      <legend class="bottom-gutter-2-3">
+        Choose the branding you’d like on your emails.
+      </legend>
+      {% if form.options.errors %}
+        <span class="error-message" data-module="track-error" data-error-type="Can’t be empty" data-error-label="{{ form.options.name }}">
+          You need to choose an option
+        </span>
+      {% endif %}
+      <div class="grid-row">
+        {% for option in form.options %}
+          <div class="column-one-quarter">
+            <label for="{{ option.id }}">
+              <img src="/static/images/branding-options/{{ option.data }}.png" alt="" class="bordered-image bottom-gutter-1-3">
+            </label>
+            {{ radio(option) }}
+          </div>
+        {% endfor %}
+      </div>
+    </fieldset>
+    <p class="form-group">
+      We’ll email you once your branding’s ready to use, or if we need any
+      more info.
+    </p>
+    {{ page_footer(
+      'Request new branding',
+      destructive=destructive,
+      back_link=url_for('.service_settings', service_id=current_service.id)
+    ) }}
+  </form>
+
+{% endblock %}