leave event (when uninviting users) does not get federated

[2chen]

Summary

When a local user invites a remote user to a local private channel and revokes the invite before the remote user has a chance to join, the initial invite event gets federated but the subsequent leave event does not get federated. This leads to a situation where the remote user sees the channel in their list of channels, but isn't able to join the channel.

Affected version

1.65 (but also all prior versions)

Steps to repro

• As user A, create a private channel
• As user A, invite a user from another homeserver to the channel
• As other user, confirm that the channel appears on the second user's list of channels, but do not join the channel
• As user A, uninvite the other user from the channel
• As the other user, there is now a persistent channel that you cannot join (although you can reject the invite)

[clokep]

Maybe similar to #1563? 🤷

[richvdh]

Duplicate of #4808