docs: [example][systemd] use `DynamicUser=yes` (#186)
This patch fixes a warning generated by some new version of systemd. Use
"User=nobody" seems to be considered unsafe. So maybe we need to fix it
in our example files.
● ratholec@hitmc.service - Rathole Client Service
Loaded: loaded (/etc/systemd/system/ratholec@.service; enabled; vendor preset: enabled)
Active: active (running) since Sat 2022-09-03 23:38:43 CST; 1h 27min ago
Main PID: 507903 (rathole)
Tasks: 14 (limit: 76731)
Memory: 6.9M
CPU: 39.908s
CGroup: /system.slice/system-ratholec.slice/ratholec@hitmc.service
└─507903 /usr/local/bin/rathole -c /etc/rathole/hitmc.toml
Sep 03 23:38:43 <hostname> systemd[1]: Started Rathole Client Service.
...
Sep 03 23:39:25 <hostname> systemd[1]: /etc/systemd/system/ratholec@.service:7: Special user nobody configured, this is not safe!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=969329
Link: https://github.com/trojan-gfw/trojan/issues/612
Link: https://www.vvave.net/archives/fix-the-systemd-error-special-user-nobody-configured-this-is-not-safe.html
inclyc