plugin XEP-0166: refactoring, and various improvments: - add models for transport and applications handlers and linked data - split models into separate file - some type hints - some documentation comments - add actions to prepare confirmation, useful to do initial parsing of all contents - application arg/kwargs and some transport data can be initialised during Jingle `initiate` call, this is notably useful when a call is made with transport data (this is the call for A/V calls where codecs and ICE candidate can be specified when starting a call) - session data can be specified during Jingle `initiate` call - new `store_in_session` argument in `_parse_elements`, which can be used to avoid race-condition when a context element (<decription> or <transport>) is being parsed for an action while an other action happens (like `transport-info`) - don't sed `sid` in `transport_elt` during a `transport-info` action anymore in `build_action`: this is specific to Jingle File Transfer and has been moved there rel 419

Those certificates are used to activate TLS for end-2-end testing (to be as
close as possible as production environment), they are used in other containers
needing TLS certificates (notably Prosody).

To generate them, minica has been used. Minica can be found at https://github.com/jsha/minica.

The following commands have been used:

$ minica --domains "server1.test,*.server1.test,server2.test,server3.test,libervia-backend.test,libervia-web.test"
$ chmod 0644 minica.pem server1.test/cert.pem && chmod 0640 server1.test/key.pem

Note that certificates are valid for 2 years and 30 days, so they must be renewed after this delay.