feat(op): add opentelemetry to token endpoint (#436)

* feat(op): add opentelemetry to token endpoint

* drop go 1.18, add 1.21, do not fail fast

pkg/op/op.go

@@ -9,6 +9,8 @@ import (
 	"github.com/gorilla/mux"
 	"github.com/gorilla/schema"
 	"github.com/rs/cors"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/trace"
 	"golang.org/x/text/language"
 	"gopkg.in/square/go-jose.v2"
 
@@ -67,6 +69,12 @@ var (
 	}
 )
 
+var tracer trace.Tracer
+
+func init() {
+	tracer = otel.Tracer("github.com/zitadel/oidc/pkg/op")
+}
+
 type OpenIDProvider interface {
 	Configuration
 	Storage() Storage