easyeffects: add option to import presets

[hauskens]

Description

• added options to import presets
• added tests
• added hausken as maintainer

Checklist

• Change is backwards compatible.

• Code formatted with ./format.

• Code tested through nix-shell --pure tests -A run.all or nix develop --ignore-environment .#all using Flakes.
  (tested with nix-shell --pure tests -A run.easyeffects-service and nix-shell --pure tests -A run.easyeffects-example-preset)

• Test cases updated/added. See example.

• Commit messages are formatted like

  {component}: {description}
  
  {long description}
  

  See CONTRIBUTING for more information and recent commit messages for examples.

• If this PR adds a new module

  • Added myself as module maintainer. See example.

Maintainer CC

@fufexan

[rycee]

Maybe this could simply be

Suggested change

	extraInputPresets = presetOptionType;
	extraOutputPresets = presetOptionType;
	extraPresets = presetOptionType;

where the "input" or "output" field inside the preset determine whether it is for input or output?

[rycee]

That is, the type of this option would be something like attrsOf presetType where presetType would be the regular JSON type with the additional requirement that it is an object containing either an "input" or "output" field. In practice I think this would look something like

presetType = let baseType = attrsOf jsonFormat.type; in baseType // {
  check = v: baseType.check v && elem (attrNames v) == [ ["input"] ["output"] ];
  description = "EasyEffects input or output JSON preset";
}

Completely untested so I'm not certain it will work very well.

[hauskens]

Thanks for the input, i really appreciate it!
I agree, it makes much more sense to have it in one attribute set, so i've modified it based on your suggestions.
I'm fairly inexperienced with programming in nix, so this feedback helped a lot.
Let me know if there is anything that comes to mind