Add a SyslogIdentifier section in .service

[CedricLevasseur]

Proposed feature

Adding a syslog identifier make the journal clearable and filterable

Rationale

It's actually unclear. For example, i'm using tomcat, and it's hard to identify it in journalctl

Apr 27 05:36:02 myhost bash[88952]: java.io.FileNotFoundException: /somewhere/logs/localhost.2022-04-27.log (Permission denied)
Apr 27 05:36:02 myhost bash[88952]: at java.io.FileOutputStream.open0(Native Method)
Apr 27 05:36:02 myhost bash[88952]: at java.io.FileOutputStream.open(FileOutputStream.java:270)
Apr 27 05:36:02 myhost bash[88952]: at java.io.FileOutputStream.<init>(FileOutputStream.java:213)

It would be clearer if it were :
Apr 27 05:36:02 myhost tomcat: java.io.FileNotFoundException: /somewhere/logs/localhost.2022-04-27.log (Permission denied)
And also i could use
journalctl -t tomcat

Additional context

Here is the source of the tip for SyslogIdentifier in systemd:
https://stackoverflow.com/a/43830129/1654749

Thank you

[CedricLevasseur]

I'm working on a Pull Request