Use CLI flags parser from Icinga Go Library

[yhabteab]

This PR replaces the manual parsing of the CLI flags with the CLI flags parser from our Icinga Go Library and cleans up the main function a bit. The flags are now parsed in daemon.ParseFlagsAndConfig function called from within main function and panics/exits when encountering unexpected inputs.

Requires

• Make project name configurable icinga-go-library#40

[julianbrost]

The flags are now parsed during initialisation of the daemon package via the magical init() GO function and panics/exits when encountering unexpected inputs.

What is the benefit of doing this in init() instead of just calling from main() like it's done so far? The latter is where I'd expect that to happen, using init() just adds code that's running implicitly but is harder to find (you couldn't set a breakpoint in main() to debug it for example). IMHO it's just very strange if programs exit before even entering main().

[yhabteab]

What is the benefit of doing this in init() instead of just calling from main() like it's done so far?

The only benefit I had from doing this was that I didn't have to explicitly make an Init call from within the main function, but now I'm going to change it though.

[oxzi]

Works as intended!

$ ./icinga-notifications --help
Usage:
  icinga-notifications [OPTIONS]

Application Options:
      --version  print version and exit
  -c, --config=  path to config file (default: /etc/icinga-notifications/config.yml)

Help Options:
  -h, --help     Show this help message

$ ./icinga-notifications --version
Icinga Notifications version: 0.0.0-gef68dc4-dirty

Build information:
  Go version: go1.22.5 (linux, amd64)
  Git commit: ef68dc48715792b1bf7d069aca9b4bdde9542c81 (modified)

System information:
  Platform: Red Star OS
  Platform version: 4.0

$ ./icinga-notifications
can't open YAML file /etc/icinga-notifications/config.yml: open /etc/icinga-notifications/config.yml: no such file or directory

$ ./icinga-notifications -c /dev/null
can't parse YAML file /dev/null: EOF

$ ./icinga-notifications --config /dev/null
can't parse YAML file /dev/null: EOF