code: private String composeContentTypeHeaderValue(HttpEndpointConfiguration endpointConfiguration) {
          return (endpointConfiguration.getContentType().contains("charset") || !StringUtils.hasText(endpointConfiguration.getCharset())) ?
                  endpointConfiguration.getContentType() :
                  endpointConfiguration.getContentType() + ";charset=" + endpointConfiguration.getCharset();
      }
docs: Creates the content type header value enriched with charset information if possible
  @param endpointConfiguration The endpoint configuration to get the content type from
  @return The content type header including charset information