core (main): Let plugins have several handlers + various improvements: `get_handler` can now return several handlers, which is notably useful for component with several included services. Various improvements such move to `async` method, docstring/type hints update, and slight improvment of SatXMPPComponent. rel 453

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