Add the allowed_mentions field to Message

[arqunis]

Discord has recently added a method of control over mentions for bots. They can prevent a mention from actually triggering a ping to a user or role, or even the @​everyone and @​here mentions. They can also dictate which mention may trigger a ping by specifying a user id or role id.

Additional information can be discovered at Discord's official documentation: https://discordapp.com/developers/docs/resources/channel#allowed-mentions-object.

[arqunis]

I did not notice that a similar issue had already been raised, making this is a duplicate. Thus, the tracking status will migrate to the first issue.