#809 rate limiter AC

[johakoch]

Added rate limiter AC

examples:

  beta_rate_limiter "rate" {
    period = "5s"
    per_period = 2
    key = "sub:${request.context.at.sub}"  #  sub claim from a jwt AC named "at"
  }

  beta_rate_limiter "rate" {
    period = "5s"
    per_period = 2
    period_window = "fixed"
    key = "ip:${request.remote_ip}"  # using new variable remote_ip
  }

---

Reviewer checklist

• Read PR description: a summary about the changes is required
• Changelog updated
• Documentation: docs/{Reference, Cli, ...}, Docker and cli help/usage
• Pulled branch, manually tested
• Verified requirements are met
• Reviewed the code
• Reviewed the related tests