errors.go
func ErrUnsupportedRequestType(st SubjectType) error {
	return ErrorResponse{
		Code:    http.StatusNotImplemented,
		Message: fmt.Sprintf("unsupported request type: %s", st),
	}
}
func ErrUnsupportedRequestType(st SubjectType) error {
	return ErrorResponse{
		Code:    http.StatusNotImplemented,
		Message: fmt.Sprintf("unsupported request type: %s", st),
	}
}
// ErrUnsupportedRequestType indicates the processor
// cannot fullfil a request for the given RequestType.