feat(op): Server interface (#447)

* first draft of a new server interface

* allow any response type

* complete interface docs

* refelct the format from the proposal

* intermediate commit with some methods implemented

* implement remaining token grant type methods

* implement remaining server methods

* error handling

* rewrite auth request validation

* define handlers, routes

* input validation and concrete handlers

* check if client credential client is authenticated

* copy and modify the routes test for the legacy server

* run integration tests against both Server and Provider

* remove unuse ValidateAuthRequestV2 function

* unit tests for error handling

* cleanup tokenHandler

* move server routest test

* unit test authorize

* handle client credentials in VerifyClient

* change code exchange route test

* finish http unit tests

* review server interface docs and spelling

* add withClient unit test

* server options

* cleanup unused GrantType method

* resolve typo comments

* make endpoints pointers to enable/disable them

* jwt profile base work

* jwt: correct the test expect

---------

Co-authored-by: Livio Spring <livio.a@gmail.com>

pkg/op/probes.go

@@ -41,9 +41,9 @@ func ReadyStorage(s Storage) ProbesFn {
 }
 
 func ok(w http.ResponseWriter) {
-	httphelper.MarshalJSON(w, status{"ok"})
+	httphelper.MarshalJSON(w, Status{"ok"})
 }
 
-type status struct {
+type Status struct {
 	Status string `json:"status,omitempty"`
 }