code: public void addSigningData(String signingMethod, String publicKeyLocation, String clearSignedMessage)
      {
          this.signingMethod = signingMethod;
          this.publicKeyLocation = publicKeyLocation;
          this.clearSignedMessage = clearSignedMessage;
          this.signed = true;
      }
docs: Adds signing data to the envelope
  
  @param signingMethod method used for signing this envelope
  @param publicKeyLocation location of the public key for the signature on this envelope
  @param clearSignedMessage clear signed message created for signing this envelope