Add code to speaker

Add unique identifier (code) to speakers within schedule JSON API
to allow speakers to be identified throughout the schedule.

vendor/symposion/schedule/views.py

@@ -222,7 +222,8 @@ def make_speaker_dict(user, speaker):
         'name': speaker.name,
         'twitter': speaker.twitter_username,
         'contact': speaker.email if has_contact_perm(user) else 'redacted',
-        'picture_url': speaker_photo(None, speaker, 120)
+        'picture_url': speaker_photo(None, speaker, 120),
+        'code': speaker.code,
     }
 
 def schedule_json(request):

vendor/symposion/speakers/models.py

@@ -157,3 +157,8 @@ class Speaker(models.Model):
             for p in self.copresentations.all():
                 presentations.append(p)
         return presentations
+
+    @property
+    def code(self):
+        """ A unique string that identifies this speaker. """
+        return f"{self.pk}"