component AP gateway: message retractation => AP deletion Convert XEP-0424 message retractation request to suitable AP delete activity. The message workflow and its triggers are now used instead of a direct observer, as it is now possible to do so with component, and this let other plugin to parse and eventually update metadata. rel 367

these certificates are used for demo purpose only. Those must be the same as in
backend_e2e (they are generated there)