code: public JWSHeader setX509Url(String x509Url) {
          this.x509Url = x509Url;
          this.put(HeaderConstants.X509_URL, x509Url);
          return this;
      }
docs: Sets the X.509 URL header parameter that is an absolute URL that refers to a resource for the
  X.509 public key certificate or certificate chain corresponding to the key used to digitally
  sign the JWS or {@code null} for none.
  
  <p>
  Overriding is only supported for the purpose of calling the super implementation and changing
  the return type, but nothing else.
  </p>