Add syslog support

Currently we don't have any way of exporting an access log. This could be implemented by supporting the syslog standard in rfc3164 and/or rfc5424 format. For the message format of access logs either the nginx or haproxy defaults could be used so it's supported by a wide variety of tools out of the box

未指定任何檔案、測試或進入點；先找出存取日誌是如何產生和匯出的。釐清需要 RFC3164、RFC5424，還是兩者，並選擇 nginx 或 haproxy 的訊息格式；完成的標準是能夠透過約定的 syslog 格式匯出存取日誌。

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