String multipartPostBlobAndVerify(HttpHeaders headers, ByteBuffer content, ByteBuffer usermetadata) throws Exception {
    HttpRequest httpRequest = RestTestUtils.createRequest(HttpMethod.POST, "/", headers);
    HttpPostRequestEncoder encoder = createEncoder(httpRequest, content, usermetadata);
    NettyClient.ResponseParts responseParts = nettyClient.sendRequest(encoder.finalizeRequest(), encoder, null).get();
    return verifyPostAndReturnBlobId(responseParts, content.capacity(), false);
  }
Posts a blob with the given {@code headers} and {@code content}.
@param headers the headers required.
@param content the content of the blob.
@param usermetadata the {@link ByteBuffer} that represents user metadata
@return the blob ID of the blob.
@throws Exception
ambry-frontend/src/integration-test/java/com/github/ambry/frontend/FrontendIntegrationTestBase.java