docs: document where Lua m.log() messages goes

content/3-reference-manual/3-2-configuration-directives.md

@@ -1146,6 +1146,12 @@ function main()
 end
 ```
 
+{{% notice note %}}
+
+m.log(level, text) writes text to the debug log (see [SecDebugLog](#secdebuglog)) if [SecDebugLogLevel](#secdebugloglevel) is set to level or higher. In ModSecurity v2, messages at levels 1–3 also always go to the Apache error log and to the audit log, whatever SecDebugLogLevel is set to. libModSecurity v3 writes them only to the debug log, never to the web server's error log or the console, and a library built with --disable-debug-logs doesn't write them at all.
+
+{{% /notice %}}
+
 In this first example we were only retrieving one variable at the time. In this case the name of the variable is known to you. In many cases, however, you will want to examine variables whose names you won't know in advance, for example script parameters.
 
 Example showing use of m.getvars() to retrieve many variables at once: