init webhook work

[maltegrosse]

Describe the pull request

General

Once a user successfully logged in, a simple webhook is sent including the subdomain. If no webhook url is given, this functionally is ignored.

Background

As I am not able to use wildcard certificates or DNS challenge for my reverse proxy (traefik), I created a simple webhook function, which sends a post internally to some small middleware api service, which handles then dynamically the https cert creation by adding routes using the subdomain name. multiple webhooks (for the same subdomain) are ignored by my middleware.

If needed I can also provide some example setup (docker-compose) of my traefik setup.

Consent

• I agree to follow the Code of Conduct by submitting this pull request.
• I have read and acknowledged the Contributing guide.
• I have added test cases to cover the new code or have provided the test plan.

Test plan

I havent added any test plans caus my limited golang knowledge - I hope someone else can assist here.