NodeBB-ActivityPub Bridge Test Instance

@julian @mro i'm indeed not aware of a normative use of Reject being described, and there is also some talk about using Reject for e.g. messages rejected by a user's policy to block messages from strangers, so those would be two quite different use cases

@mro @renchap @julian @trwnh Mastodon did not reject the post, but rather failed halfway processing it because it was malformed; in other words, the failure was not intentional, a bug in NodeBB triggered a bug in Mastodon