Try adding some format options

Something like this would allow the user to force a format while giving them the option to obtain gifs.
(forceFmt is set to true by default to try and preserve current behavior)

disco/types/user.py

@@ -22,11 +22,17 @@ class User(SlottedModel, with_equality('id'), with_hash('id')):
 
     presence = Field(None)
 
-    def get_avatar_url(self, fmt=None, size=1024):
+    def get_avatar_url(self, fmt=None, force_fmt=True, size=1024):
         if not self.avatar:
             return 'https://cdn.discordapp.com/embed/avatars/{}.png'.format(self.default_avatar.value)
         if fmt is not None:
-            return 'https://cdn.discordapp.com/avatars/{}/{}.{}?size={}'.format(self.id, self.avatar, fmt, size)
+            if force_fmt is False:
+                if self.avatar.startswith('a_'):
+                    return 'https://cdn.discordapp.com/avatars/{}/{}.gif?size={}'.format(self.id, self.avatar, size)
+                else:
+                    return 'https://cdn.discordapp.com/avatars/{}/{}.{}?size={}'.format(self.id, self.avatar, fmt, size)
+            else:
+                return 'https://cdn.discordapp.com/avatars/{}/{}.{}?size={}'.format(self.id, self.avatar, fmt, size)
         if self.avatar.startswith('a_'):
             return 'https://cdn.discordapp.com/avatars/{}/{}.gif?size={}'.format(self.id, self.avatar, size)
         else: