nixos/earlyoom: bring the module up to date

[ncfavier]

Removes deprecated option ignoreOOMScoreAdjust, introduces killHook as a replacement for notificationsCommand, and adds an extraArgs option for things not covered by the module.

Fixes #132783
Fixes #83504

Untested.

My example killHook script sucks, suggestions welcome.

[ncfavier]

cc @deliciouslytyped as I can't add you to reviewers for some reason

[Profpatsch]

Tried on my very simple configuration

    services.earlyoom = {
      enable = true;
      freeMemThreshold = 5; # <5% free
    };

and it still seems to work.

[ncfavier]

Rebased after #130003, cc @peterhoeg

[peterhoeg]

Haven't tested it, but the changes look good to me. killHook sample is fine. How about a super simple nixos test that simply verifies that it launches?

[ncfavier]

Sounds like a good opportunity to write my first NixOS test

[ncfavier]

Relaxed the type of free{Mem,Swap}Threshold to fix #83504, and added reportInterval to avoid log flooding (the interval defaults to one second when not using upstream's config file... rfjakob/earlyoom#177 (comment)).

Tested locally, works fine.
@ofborg test earlyoom

[peterhoeg]

I don't like the string bit at all as we have no way of verifying that we're passing a sane value through.

Instead add 2 new integer options for the corresponding kill values and use those to generate the proper string.

[ncfavier]

You're right, I was lazy.

Tested again with the new options.

[peterhoeg]

@GrahamcOfBorg build earlyoom.passthru.tests