[captcha] Support multple domains

[LaurenceJJones]

As from user issue in reddit has outlined a limitation in the current lua implementation. My thoughts so far is we could expose a configuration which looks like:

captcha:
   - host: my.domain.net
     site_key: xyz
     site_secret: secret
     provider: recaptcha
   - host: my.domain.com
     site_key: xyz
     site_secret: secret
     provider: recaptcha
  - host: *.service.host
     site_key: xyz
     site_secret: secret
     provider: turnstile

The host is the host header that matches on either a string or a globbing pattern and then is served a template from this. However, each site will most likely want to grant a grace period per domain.

I havent even started working on Captcha side yet, so I dont know if this is achievable let alone how the template will be served.