[Federation]: private multi-messages are not delivered

Description

I already reporter this to @dansup a year ago as a privacy vulnerability bug by email and the bug itself is fixed now.

But if you write a direct message to 2 pixelfed accounts , it's not delivered to the accounts

Screenshot of the message

It's not in the inbox and not in the requests.

This was already reported here.

But as this was closed and as in v0.14.2 the new multi chat feature was "newly released" - here is again the bug report

Steps to reproduce

1. Write a direct message from Mastodon to two Pixelfed instances
2. See that the direct message is not delivered

It doesn't matter if there is a picture in the message or not.

Pixelfed version

0.14.2

Acknowledgements

Yes