Session start and end events

[breedx-splk]

Changes

This serves as an alternative/successor to #1042. Instead of describing a session change event, we have a session start and session end event instead.

Merge requirement checklist

• CONTRIBUTING.md guidelines followed.
• Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• schema-next.yaml updated with changes to existing conventions.

[bidetofevil]

LGTM. One non-blocking question, and a suggestion to mention how the previous session ID can be used to signify that the previous session has ended - but again, non-blocking

[joaopgrassi]

@breedx-splk I think it would be good to have folks from the event and client working groups to take a look and approve this? Are you in touch with them? We don't seem to have a GitHub team for them so not sure how to get attention.

[scheler]

Mostly looks good, left a couple comments. I envision having named sessions in the long term, but it can be added in the future using a session.name field.

[breedx-splk]

3 approvals, are we waiting for anything else on this? 🙏🏻

[lmolkova]

@breedx-splk please resolve open discussions (if they are resolved) and it should be ready to go