src/Signer.php
public function sign($message)
    {
        $signatureParameters = $this->signatureParameters($message);
        $message = $message->withAddedHeader('Signature', $signatureParameters->string());
        $message = $message->withAddedHeader('Authorization', 'Signature '.$signatureParameters->string());

        return $message;
    }
public function sign($message)
    {
        $signatureParameters = $this->signatureParameters($message);
        $message = $message->withAddedHeader('Signature', $signatureParameters->string());
        $message = $message->withAddedHeader('Authorization', 'Signature '.$signatureParameters->string());

        return $message;
    }
@param RequestInterface $message

@return RequestInterface