code: protected Response customOperation(final String resource, final RequestTypeEnum requestType, final String id,
              final String operationName, final RestOperationTypeEnum operationType)
              throws IOException {
          final Builder request = getResourceRequest(requestType, operationType).resource(resource).id(id);
          return execute(request, operationName);
      }
docs: Execute a custom operation
  
  @param resource the resource to create
  @param requestType the type of request
  @param id the id of the resource on which to perform the operation
  @param operationName the name of the operation to execute
  @param operationType the rest operation type
  @return the response
  @see <a href="https://www.hl7.org/fhir/operations.html">https://www.hl7.org/fhir/operations.html</a>