Don’t ask for a user’s email address if we know it

If a user is logged in then we already know their name and email
address. So there’s no need for them to fill them again on the support
form.

One concern we might have about this is the user not realising we’re
doing this, and the feedback form looking like a bit of a black hole.
So we’re replaying their email address on this page to reassure them
that:
- we know who they are
- and that they’ll get a reply

app/templates/views/support/problem.html

@@ -22,10 +22,14 @@
         <p>What went wrong, if anything? What went well? How could we improve this service?</p>
         <form method="post">
             {{ textbox(form.feedback, width='1-1', hint='', rows=10) }}
-            <h3 class="heading-medium">Do you want a reply?</h3>
-            <p>Leave your details below if you'd like a response.</p>
-            {{ textbox(form.name, width='1-1') }}
-            {{ textbox(form.email_address, width='1-1') }}
+            {% if not current_user.is_authenticated %}
+              <h3 class="heading-medium">Do you want a reply?</h3>
+              <p>Leave your details below if you'd like a response.</p>
+              {{ textbox(form.name, width='1-1') }}
+              {{ textbox(form.email_address, width='1-1') }}
+            {% else %}
+              <p>We’ll reply to {{ current_user.email_address }}</p>
+            {% endif %}
             {{ page_footer(
               'Send',
               secondary_link=url_for('.support'),