This PR removes multiple unneeded fields from the `HookTask` struct and adds the two headers `X-Hub-Signature` and `X-Hub-Signature-256`.
## ⚠️ BREAKING ⚠️
* The `Secret` field is no longer passed as part of the payload.
* "Breaking" change (or fix?): The webhook history shows the real called url and not the url registered in the webhook (`deliver.go`@129).
Close#16115Fixes#7788Fixes#11755
Co-authored-by: zeripath <art27@cantab.net>
* Added tests for MS Teams.
* Added tests for Dingtalk.
* Added tests for Telegram.
* Added tests for Feishu.
* Added tests for Discord.
* Added tests for closed issue and pullrequest comment.
* Added tests for Matrix.
* Trim all spaces.
* Added tests for Slack.
* Added JSONPayload tests.
* Added general tests.
* Replaced duplicated code.
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
