Use syslog to manage caddy std{out,err} on FreeBSD (#2652)

* Use syslog to manage caddy std{out,err} on FreeBSD

There is no good way to rotate the logfile created by the previous
FreeBSD rc.d script (it's the result of redirecting std{out,err} and
is held open by the shell).

This solves the problem by sending caddy's std{out,err} stream to
syslog, using the daemon command's builtin functionality.

It replaces the old `caddy_logfile` rc.conf variable with
`caddy_syslog_facility` (which defaults to 'local7') and
`caddy_syslog_level` (which defaults to 'notice').

By default, these messages will end up in /var/log/messages but can
be redirected as documented in the script's comments.

* Add info about rotating log with newsyslog

If you create a caddy specific logfile in `/var/log`, you should
rotate it.

This adds a bit of info to the dist/init/freebsd/README.md about
rotating that log file with newsyslog.

dist/init/freebsd/README.md

+# Logging the caddy process's output:
+
+Caddy's FreeBSD `rc.d` script uses `daemon` to run `caddy`; by default
+it sends the process's standard output and error to syslog with the
+`caddy` tag, the `local7` facility and the `notice` level.
+
+The stock FreeBSD `/etc/syslog.conf` has a line near the top that
+captures nearly anything logged at the `notice` level or higher and
+sends it to `/var/log/messages`.  That line will send the caddy
+process's output to `/var/log/messages`.
+
+The simplest way to send `caddy` output to a separate file is:
+
+- Arrange to log the messages at a lower level so that they slip past
+  that early rule, e.g. add an `/etc/rc.conf` entry like
+
+  ``` shell
+  caddy_syslog_level="info"
+  ```
+
+- Add a rule that catches them, e.g. by creating a
+  `/usr/local/etc/syslog.d/caddy.conf` file that contains:
+
+  ```
+  # Capture all messages tagged with "caddy" and send them to /var/log/caddy.log
+  !caddy
+  *.*      /var/log/caddy.log
+  ```
+
+  Heads up, if you specify a file that does not already exist, you'll
+  need to create it.
+
+-  Rotate `/var/log/caddy.log` with `newsyslog` by creating a
+  `/usr/local/etc/newsyslog.conf/caddy.conf` file that contains:
+
+  ```
+  # See newsyslog.conf(5) for details.  Logs written by syslog,
+  # no need for a pidfile or signal, the defaults workg.
+  # logfilename         [owner:group]  mode count size when  flags [/pid_file] [sig_num]
+  /var/log/caddy.log        www:www       664  7     *    @T00  J
+  ```
+
+There are many other ways to do it, read the `syslogd.conf` and
+`newsyslog.conf` man pages for additional information.

dist/init/freebsd/caddy

@@ -29,8 +29,13 @@
 # caddy_group (str):  	      Set to "wheel" by default.
 #                             Defines the group that caddy files will be attached to
 #
-# caddy_logfile (str)	      Set to "/var/log/caddy.log" by default.
-#			      Defines where the process log file is written, this is not a web access log
+# caddy_syslog_facility (str) Set to "local7" by default.
+#                             Defines the syslog facility used to log output from the caddy process.
+#                             This is NOT the web access log.
+#
+# caddy_syslog_level (str)    Set to "notice" by default.
+#                             Defines the syslog level used to log output from the caddy process.
+#                             This is NOT the web access log.
 #
 # caddy_env (str)	      Set to "" by default.
 #			      This allows environment variable to be set that may be required, for example when using "DNS Challenge" account credentials are required.
@@ -49,7 +54,8 @@ load_rc_config ${name}
 : ${caddy_bin_path="/usr/local/bin/caddy"}
 : ${caddy_cpu="99%"} # was a bug for me that caused a crash within jails
 : ${caddy_config_path="/usr/local/www/Caddyfile"}
-: ${caddy_logfile="/var/log/caddy.log"}
+: ${caddy_syslog_facility="local7"}
+: ${caddy_syslog_level="notice"}
 : ${caddy_user="root"}
 : ${caddy_group="wheel"}
 
@@ -62,7 +68,7 @@ fi
 pidfile="/var/run/${name}.pid"
 procname="${caddy_bin_path}" #enabled builtin pid checking for start / stop
 command="/usr/sbin/daemon"
-command_args="-p ${pidfile} /usr/bin/env ${caddy_env} ${procname} -cpu ${caddy_cpu} -log stdout -conf ${caddy_config_path} -agree -email ${caddy_cert_email} < /dev/null >> ${caddy_logfile} 2>&1"
+command_args="-p ${pidfile} -T ${name} -l ${caddy_syslog_facility} -s ${caddy_syslog_level} /usr/bin/env ${caddy_env} ${procname} -cpu ${caddy_cpu} -log stdout -conf ${caddy_config_path} -agree -email ${caddy_cert_email} < /dev/null"
 
 start_precmd="caddy_startprecmd"
 
@@ -71,10 +77,6 @@ caddy_startprecmd()
 	if [ ! -e "${pidfile}" ]; then
 		install -o "${caddy_user}" -g "${caddy_group}" "/dev/null" "${pidfile}"
 	fi
-
-	if [ ! -e "${caddy_logfile}" ]; then
-		install -o "${caddy_user}" -g "${caddy_group}" "/dev/null" "${caddy_logfile}"
-	fi
 }
 
 required_files="${caddy_config_path}"