feat: Token Revocation, Request Object and OP Certification (#130)

FEATURES (and FIXES):
- support OAuth 2.0 Token Revocation [RFC 7009](https://datatracker.ietf.org/doc/html/rfc7009)
- handle request object using `request` parameter [OIDC Core 1.0 Request Object](https://openid.net/specs/openid-connect-core-1_0.html#RequestObject)
- handle response mode
- added some information to the discovery endpoint:
  - revocation_endpoint (added with token revocation) 
  - revocation_endpoint_auth_methods_supported (added with token revocation)
  - revocation_endpoint_auth_signing_alg_values_supported (added with token revocation)
  - token_endpoint_auth_signing_alg_values_supported (was missing)
  - introspection_endpoint_auth_signing_alg_values_supported (was missing)
  - request_object_signing_alg_values_supported (added with request object)
  - request_parameter_supported (added with request object)
 - fixed `removeUserinfoScopes ` now returns the scopes without "userinfo" scopes (profile, email, phone, addedd) [source diff](https://github.com/caos/oidc/pull/130/files#diff-fad50c8c0f065d4dbc49d6c6a38f09c992c8f5d651a479ba00e31b500543559eL170-R171)
- improved error handling (pkg/oidc/error.go) and fixed some wrong OAuth errors (e.g. `invalid_grant` instead of `invalid_request`)
- improved MarshalJSON and added MarshalJSONWithStatus
- removed deprecated PEM decryption from `BytesToPrivateKey`  [source diff](https://github.com/caos/oidc/pull/130/files#diff-fe246e428e399ccff599627c71764de51387b60b4df84c67de3febd0954e859bL11-L19)
- NewAccessTokenVerifier now uses correct (internal) `accessTokenVerifier` [source diff](https://github.com/caos/oidc/pull/130/files#diff-3a01c7500ead8f35448456ef231c7c22f8d291710936cac91de5edeef52ffc72L52-R52)

BREAKING CHANGE:
- move functions from `utils` package into separate packages
- added various methods to the (OP) `Configuration` interface [source diff](https://github.com/caos/oidc/pull/130/files#diff-2538e0dfc772fdc37f057aecd6fcc2943f516c24e8be794cce0e368a26d20a82R19-R32)
- added revocationEndpoint to `WithCustomEndpoints ` [source diff](https://github.com/caos/oidc/pull/130/files#diff-19ae13a743eb7cebbb96492798b1bec556673eb6236b1387e38d722900bae1c3L355-R391)
- remove unnecessary context parameter from JWTProfileExchange [source diff](https://github.com/caos/oidc/pull/130/files#diff-4ed8f6affa4a9631fa8a034b3d5752fbb6a819107141aae00029014e950f7b4cL14)

pkg/op/userinfo.go

@@ -6,12 +6,12 @@ import (
 	"net/http"
 	"strings"
 
+	httphelper "github.com/caos/oidc/pkg/http"
 	"github.com/caos/oidc/pkg/oidc"
-	"github.com/caos/oidc/pkg/utils"
 )
 
 type UserinfoProvider interface {
-	Decoder() utils.Decoder
+	Decoder() httphelper.Decoder
 	Crypto() Crypto
 	Storage() Storage
 	AccessTokenVerifier() AccessTokenVerifier
@@ -37,14 +37,13 @@ func Userinfo(w http.ResponseWriter, r *http.Request, userinfoProvider UserinfoP
 	info := oidc.NewUserInfo()
 	err = userinfoProvider.Storage().SetUserinfoFromToken(r.Context(), info, tokenID, subject, r.Header.Get("origin"))
 	if err != nil {
-		w.WriteHeader(http.StatusForbidden)
-		utils.MarshalJSON(w, err)
+		httphelper.MarshalJSONWithStatus(w, err, http.StatusForbidden)
 		return
 	}
-	utils.MarshalJSON(w, info)
+	httphelper.MarshalJSON(w, info)
 }
 
-func ParseUserinfoRequest(r *http.Request, decoder utils.Decoder) (string, error) {
+func ParseUserinfoRequest(r *http.Request, decoder httphelper.Decoder) (string, error) {
 	accessToken, err := getAccessToken(r)
 	if err == nil {
 		return accessToken, nil