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/utils/http.go

@@ -1,107 +0,0 @@
-package utils
-
-import (
-	"context"
-	"encoding/json"
-	"fmt"
-	"io/ioutil"
-	"log"
-	"net/http"
-	"net/url"
-	"strings"
-	"time"
-)
-
-var (
-	DefaultHTTPClient = &http.Client{
-		Timeout: time.Duration(30 * time.Second),
-	}
-)
-
-type Decoder interface {
-	Decode(dst interface{}, src map[string][]string) error
-}
-type Encoder interface {
-	Encode(src interface{}, dst map[string][]string) error
-}
-
-type FormAuthorization func(url.Values)
-type RequestAuthorization func(*http.Request)
-
-func AuthorizeBasic(user, password string) RequestAuthorization {
-	return func(req *http.Request) {
-		req.SetBasicAuth(url.QueryEscape(user), url.QueryEscape(password))
-	}
-}
-
-func FormRequest(endpoint string, request interface{}, encoder Encoder, authFn interface{}) (*http.Request, error) {
-	form := url.Values{}
-	if err := encoder.Encode(request, form); err != nil {
-		return nil, err
-	}
-	if fn, ok := authFn.(FormAuthorization); ok {
-		fn(form)
-	}
-	body := strings.NewReader(form.Encode())
-	req, err := http.NewRequest("POST", endpoint, body)
-	if err != nil {
-		return nil, err
-	}
-	if fn, ok := authFn.(RequestAuthorization); ok {
-		fn(req)
-	}
-	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")
-	return req, nil
-}
-
-func HttpRequest(client *http.Client, req *http.Request, response interface{}) error {
-	resp, err := client.Do(req)
-	if err != nil {
-		return err
-	}
-	defer resp.Body.Close()
-
-	body, err := ioutil.ReadAll(resp.Body)
-	if err != nil {
-		return fmt.Errorf("unable to read response body: %v", err)
-	}
-
-	if resp.StatusCode != http.StatusOK {
-		return fmt.Errorf("http status not ok: %s %s", resp.Status, body)
-	}
-
-	err = json.Unmarshal(body, response)
-	if err != nil {
-		return fmt.Errorf("failed to unmarshal response: %v %s", err, body)
-	}
-	return nil
-}
-
-func URLEncodeResponse(resp interface{}, encoder Encoder) (string, error) {
-	values := make(map[string][]string)
-	err := encoder.Encode(resp, values)
-	if err != nil {
-		return "", err
-	}
-	v := url.Values(values)
-	return v.Encode(), nil
-}
-
-func StartServer(ctx context.Context, port string) {
-	server := &http.Server{Addr: port}
-	go func() {
-		if err := server.ListenAndServe(); err != http.ErrServerClosed {
-			log.Fatalf("ListenAndServe(): %v", err)
-		}
-	}()
-
-	go func() {
-		<-ctx.Done()
-		ctxShutdown, cancelShutdown := context.WithTimeout(context.Background(), 5*time.Second)
-		defer cancelShutdown()
-		err := server.Shutdown(ctxShutdown)
-		if err != nil {
-			log.Fatalf("Shutdown(): %v", err)
-		}
-	}()
-}