Add usernames to the email sent to the secretariat when a possible duplicate person has been detected. Fixes ietf-tools#2307. Commit ready for merge.

 - Legacy-Id: 13503

Author: rjsparks

ietf/templates/person/mail/possible_duplicates.txt

@@ -9,9 +9,10 @@ There are now {{persons|length}} Person objects sharing that name.
 Please check to see if they represent the same actual person, and if so, merge the objects as appropriate.
 
 {% for person in persons %}Person {{forloop.counter}} {{ person.name }} (pk={{person.pk}})
-    time:    {{person.time}}
-    ascii:   {{person.ascii}}
-    email:   {% for email in person.email_set.all %}{{ email.address }} {% endfor %}
-    aliases: {{ person.alias_set.all|join:", " }}
+    time:     {{person.time}}
+    ascii:    {{person.ascii}}
+    email:    {% for email in person.email_set.all %}{{ email.address }} {% endfor %}
+    aliases:  {{ person.alias_set.all|join:", " }}
+    username: {% if person.user %}{{person.user.username}}{% else %}None{% endif %}
 
 {% endfor %} {% endautoescape %}