- add a `jingle_preflight_info` method in the Jingle Application model to handle this kind
of information
- XEP-0353 is calling `jingle_preflight_info` when a `ringing` message is received
- XEP-0167 use this information to send a `ringing` info to frontends
- XEP-0166: add `jingle_preflight` and `jingle_preflight_cancel` methods to prepare a
jingle session, principally used by XEP-0353 to create and cancel a session
- XEP-0167: preflight methods implementation, workflow split in more methods/signals to
handle UI and call events (e.g.: retract or reject a call)
- XEP-0234: implementation of preflight methods as they are now mandatory
- XEP-0353: handle various events using the new preflight methods
rel 423
- a new `jingle_terminate` bridge method let frontend terminate a session
- methods to manage a session from another plugin
- methods to parse `<reason>` element from another plugin
- allow session to be created before a first jingle request is received, to prepare for
`preflight` methods
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