XMPP user should be able to block an ActivityPub user and to delete an
item
Milestone(s)
- Implement XEP-0191: Blocking Command in Libervia and its ActivityPub
component
- link Pubsub item retraction to delete activity
- implement XEP-0424: Message Retraction in Libervia and its
ActivityPub component (for private messages)
- CLI commands to do user blocking and message retraction
- tests (either unit test or e2e)