This option used to log custom information about the master
transaction. For example, an admin may configure Squid to log
which "user group" the transaction belongs to, where "user group"
will be determined based on a set of ACLs and not [just]
authentication information.
Values of key/value pairs can be logged using %{key}note macros:
note key value acl ...
logformat myFormat ... %{key}note ...
This clause only supports fast acl types.
See https://wiki.squid-cache.org/SquidFaq/SquidAcl for details.