public Content postContent(byte[] buf, MediaType contentType) throws IOException, UnsuccessfulRequestException {
        return postContent(buf, contentType, null);
    }
POSTs GZIP compressed content to bytebin.

@param buf the compressed content
@param contentType the type of the content
@param userAgentExtra extra string to append to the user agent
@return the key of the resultant content
@throws IOException if an error occurs
common/src/main/java/me/lucko/luckperms/common/http/BytebinClient.java