9e2df2478b
A participation activity is now addressed to the Festipod app actor alone and handled on reception in the app's inbox, the way the ActivityPods developer advised: use the ActivityPub protocol rather than a side channel. Any compatible sender may deliver; the inbox accepts only the activity's own signer, and the backend still requires the activity to lie in that actor's pod and acts on the stored copy. The meeting point is read again in its creator's pod before anything is written: read through the participant's pod, a foreign server's proxy chose the attendee list and the notification's name. Confidentiality is unchanged: the Join stays readable by its author and the app only. Recorded in decision_2026-11-03_participation-delivered-to-the-app, a named exception to festipod-only-reference-app-patterns.