fix: do not store stacktrace in sentinel errors (#823)

Author: mitar

errors.go

@@ -22,10 +22,10 @@ import (
 var (
 	// ErrInvalidatedAuthorizeCode is an error indicating that an authorization code has been
 	// used previously.
-	ErrInvalidatedAuthorizeCode = errors.New("Authorization code has ben invalidated")
+	ErrInvalidatedAuthorizeCode = stderr.New("Authorization code has ben invalidated")
 	// ErrSerializationFailure is an error indicating that the transactional capable storage could not guarantee
 	// consistency of Update & Delete operations on the same rows between multiple sessions.
-	ErrSerializationFailure = errors.New("The request could not be completed due to concurrent access")
+	ErrSerializationFailure = stderr.New("The request could not be completed due to concurrent access")
 	ErrUnknownRequest       = &RFC6749Error{
 		ErrorField:       errUnknownErrorName,
 		DescriptionField: "The handler is not responsible for this request.",