[#83211730] Fixing TeamSnap event webhooks.

- Fixed an issue where adding a group to an existing event would not trigger the correct actions.
- Fixed an issue where multiple events would be created for a unique event, if a game was made with more than one competitor.
- Fixed an issue where the response was not being decoded correctly after sending an initial request to TeamSnap for a game event with competitors.
- Moved group check to TeamSnap webhook template and added check to each unique webhooks `process()`
- Fixed typos in comments

Requires: https://github.com/AllPlayers/allplayers-mainline/pull/4118
That is referring to the possibility that each webhook may be canceled here: https://github.com/AllPlayers/service-webhooks/blob/83211730-webhook_event_fix/lib/AllPlayers/Webhooks/Teamsnap/SimpleWebhook.php#L324-L327

That is in every TeamSnap webhook, would you like it to say: `Proceed only if this webhook was not canceled`