sysstat init file is heavily broken

Maintainer: @neheb @krant @ratkaj
Environment: x86_64 23.05.5 / 24.10.0-rc2

Description:

Init file is broken. https://github.com/openwrt/packages/blob/master/utils/sysstat/files/sysstat.init

1. Must use /var/log/sa instead of /var/log/sysstat for compatibility with sar hardcoded value /var/log/sa.
2. Line 26 [ -d /var/log/sysstat ] || mkdir -p /var/log/sysstat must use a non hardcoded variable $sa_dir.
3. Line 37 procd_set_param command $PROG -S DISK -F -L - does not run:

# /usr/lib/sysstat/sadc -S DISK -F -L -
Cannot open /var/log/sa/sa15: No such file or directory

It has to include $sa_dir variable and do not include -, like this may be:

/usr/lib/sysstat/sadc -S DISK -F -L 1 $sa_dir

Also it has to include an interval variable, from config file possibly.

4. Lines 28-34:

{
		echo "HISTORY=$log_history"
		echo "COMPRESSAFTER=$compressafter"
		echo "SADC_OPTIONS=\"$sadc_options\""
		echo "ZIP=\"$zip\""
		echo "ENABLED=\"$enabled\""
	} > $SYSSTAT_CFG

The config file is getting overwritten every time and thus truncated to a limited number of parameters, why?

Currently service starts but does not work:

# /etc/init.d/sysstat status
running
# service |grep sysstat
/etc/init.d/sysstat           	   enabled	   stopped

Cannot figure out how to fix it by myself properly for now.

Read utils/sysstat/files/sysstat.init and compare its log directory, sadc command, interval, and config-writing behavior with the issue's examples. Reproduce the service and status commands on OpenWrt, then verify that the service uses /var/log/sa, passes the configured interval and directory to sadc, and preserves the required config values.