Same perl replacement as https://github.com/go-gitea/gitea/pull/25686 but for 1.20 to ease future backporting.
Currently we can add webhooks for organizations but not for users. This PR adds the latter. You can access it from the current users settings. ![grafik](https://user-images.githubusercontent.com/1666336/197391408-15dfdc23-b476-4d0c-82f7-9bc9b065988f.png)