Other evaluator types

[Sebbs128]

There are possibilities for other useful types of evaluators. Some are

• Count evaluators
  • for example, number of cookies, headers, etc, either by a specific name (via Selector) or count of all (Selector = "")
  • this is useful for imposing limits, or for duplicate (/forgery/bypass) detection
• web socket-specific evaluators
  • some investigation/discussion required here on whether this is needed or possible
    • Taking inspiration/guidance from Azure WAF's (when used with Front Door at least) doesn't help here as Front Door doesn't support proxying web socket connections, but is something YARP is capable of

This issue is for initial suggestions and initial discussion of other evaluators (including the two mentioned here) to include in this project.