Allow change json of webhooks

[Rayzggz]

Is it a duplicate question?
No

Is your feature request related to a problem? Please describe.
Yes
I want to send the notification to DingTalk Bot. But the Webhook json is different between uptime-kuma and DingTalk Bot.

Describe the solution you'd like
In uptimerobot.com , I can add WebHook and set the POST Value.
uptimerobot.com will send the json by my format.
And the json context will replaced by some variables such as monitorID alertDetails

Describe alternatives you've considered
Now, I write a PHP to receive the webhook from uptime-kuma and change the format that is DingTalk Bot required.

Additional context

[CommanderStorm]

@Rayzggz
I think this is a duplicate of #975
If you agree, could you please close this Issue, as duplicates only create immortal zombies and are really hard to issue-manage?
If not, what makes this issue unique enough to require an additional issue? (Could this be integrated into the issue linked above?) ^^

This could also have been resolved by #3088 which was merged into the 1.23 release