Clarify use_username_as_clientid is not global

man/mosquitto.conf.5.xml

@@ -1263,6 +1263,7 @@ log_timestamp_format %Y-%m-%dT%H:%M:%S
 							disconnected as not authorised when this option is
 							set to true. Do not use in conjunction with
 							<option>clientid_prefixes</option>.</para>
+						<para>This does not apply globally, but on a per-listener basis.</para>
 						<para>See also
 							<option>use_identity_as_username</option>.</para>
 						<para>Not reloaded on reload signal.</para>

mosquitto.conf

@@ -290,6 +290,7 @@
 # authorised when this option is set to true.
 # Do not use in conjunction with clientid_prefixes.
 # See also use_identity_as_username.
+# This does not apply globally, but on a per-listener basis.
 #use_username_as_clientid
 
 # Change the websockets headers size. This is a global option, it is not