Proposal: Debug API

[ecordell]

When developing rules for the proxy, it can be frustrating to get no information back out for a failed request that you expected to succeed.

We could provide an API, kind of like SubjectAccessReview, that client can talk to debug a request.

Strawman design:

apiVersion: authzed.com/v1alpha1
kind: ProxyRuleDebug
spec:
  verb: get | list | etc
  resource: pods
  apiVersion: v1
  # for requests that require a body:
  body:
      apiVersion: v1
      kind: Pod
      spec:
         containers: [ ... ]
status:
   matchedRules:
    # showing the check resolved from the request
   - check: namespace:foo#create_pod@user:evan.  
     result: false
   # show the list of values generated as a prefilter
   - prefilter: 
      - foo/bar
      - foo/baz
      - foo2/baz2

This new API should be protected; perhaps by requiring an annotation with a specific preshared key:

apiVersion: authzed.com/v1alpha1
kind: ProxyRuleDebug
metadata:
   annotations:
      authzed.com/proxy-debug-key: as13nasdf0jasfd
spec:
... 

Note that for this to provide detailed debug info, it should run the actual request; i.e. any writes will result in changes to the backing SpiceDB and kube-apiserver.

Like SubjectAccessReview, this object isn't stored anywhere, the response is ephemeral.