code: public CertificateBundle mergeCertificate(MergeCertificateRequest mergeCertificateRequest) {
          return mergeCertificate(mergeCertificateRequest.vaultBaseUrl(), mergeCertificateRequest.certificateName(),
                  mergeCertificateRequest.x509Certificates(), mergeCertificateRequest.certificateAttributes(),
                  mergeCertificateRequest.tags());
      }
docs: Merges a certificate or a certificate chain with a key pair existing on the
  server.
  
  @param mergeCertificateRequest
  the grouped properties for merging a certificate request
  @return the CertificateBundle if successful.