private boolean isSurroundedBy(String value, String preSuffix) {
    return value.length() > 1 && value.startsWith(preSuffix) && value.endsWith(preSuffix);
  }
Construct an {@code AbstractHttpMessageConverter} that can read mulitpart/form-data.

@param bufSize The size of the buffer (in bytes) to read the HTTP multipart body.
form-spring/src/main/java/feign/form/spring/converter/SpringManyMultipartFilesReader.java