What type of PR is this?

• bug

What this PR does / why we need it:

Current webrt-events API version defined, as mandatory, fields inside the data object, not the data object itself, so this lead to an incorrect API representation.

Moreover, callback events must include data relevant to their use cases, so it is required to dive into the required data notified. In consequence, this PR tries to cover the data required on each specific event.

Which issue(s) this PR fixes:

Fixes #84

Special notes for reviewers:

Based on the solution purposed by @teikuran , with some addons:

• Events now include a data field as mandatory
• EventRegistrationEnds also requires now a data field
• This data depend on the event, so...
  • MediaSessionInfonration was renamed to prototype MediaSession, that requires mediaSessionId
  • And this prototype is then detailed per each event:
    • MediaSessionStatusUpdate, used by EventSessionStatus requires status field
    • MediaSessionInvite, used by EventSessionInvitation requires originatorAddress and receiverAddress fields

Changelog input

 release-note - webrtc-events
- fix: Updated mandatory fields per specific event data callback

Additional documentation

n/a