Tweaked meetecho URLs, with new template string formatting filter.

- Legacy-Id: 11689

ietf/templates/meeting/agenda.html

@@ -335,7 +335,7 @@
 			<!-- Video stream (meetecho) -->
 			{% if item.timeslot.location.video_stream_url %}
 			  <a class="btn btn-default btn-xs"
-			    href="{{ item.timeslot.location.video_stream_url }}"
+			    href="{{ item.timeslot.location.video_stream_url|format:item.session }}"
 			    title="Meetecho video stream"><span class="fa fa-video-camera"></span>
 			  </a>
 			{% endif %}

ietf/utils/templatetags/textfilters.py

@@ -16,3 +16,13 @@ def xslugify(value):
     lowercase.  Also strips leading and trailing whitespace.
     """
     return _xslugify(value)
+
+@register.filter(is_safe=True)
+@stringfilter
+def format(format, values):
+    if not isinstance(values, dict):
+        tmp = {}
+        for f in values._meta.fields:
+            tmp[f.name] = getattr(values, f.name)
+        values = tmp
+    return format.format(**values)