component AP gateway: when a repeated blog post is retracted, it converted to suitable Activity: when a retract item is received, the former item is now retrieve from cache, and if it was a "repeat" blog post, it is converted to the suitable `Undo` of `Announce` activity (instead of the default `Delete` activity). rel 370

version: "3.6"
services:

  prosody:
    image: libervia/prosody:demo
    build: prosody-demo

  backend:
    image: libervia/backend:dev-demo
    build: backend-dev-demo

  web:
    image: libervia/web:dev-demo
    build: libervia-web-dev-demo