Issue description

How apisix can send log to aliyun? I think ailiyun support syslog standard rfc5424( https://help.aliyun.com/document_detail/112903.html?spm=a2c4g.11186623.6.763.28801b47aqgVZq).

But the nginx support syslog standard rfc3164(http://nginx.org/en/docs/syslog.html).

And I can not find the log message format filed "STRUCTURED-DATA" in rfc3164(https://tools.ietf.org/html/rfc3164#section-4.1.1 ),But find it in rfc5424(https://tools.ietf.org/html/rfc5424?spm=a2c4g.11186623.2.17.5b0f1b47l82QJg).

So I am confused how should I use it in syslog plugin.

Environment

• apisix version (cmd: apisix version):
• OS: