Enable `golangci-lint`

[qwerty287]

Enable https://golangci-lint.run and fix the issues it found.

If you don't like any of these linters, I'm happy to disable them and revert the changes related to them, but in general I think all I enabled now are useful.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 74.50980% with 13 lines in your changes are missing coverage. Please review.

Project coverage is 42.46%. Comparing base (0181922) to head (7bad1bb).

Files	Patch %	Lines
cmd/stubs/api/main.go	0.00%	11 Missing :warning:
pkg/api/v2/recipe.go	90.00%	1 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #12 +/- ## =========================================== - Coverage 94.39% 42.46% -51.93% =========================================== Files 9 12 +3 Lines 214 471 +257 =========================================== - Hits 202 200 -2 - Misses 6 265 +259 Partials 6 6 ``` | [Flag](https://app.codecov.io/gh/NoUmlautsAllowed/gocook/pull/12/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/NoUmlautsAllowed/gocook/pull/12/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | `42.46% <74.50%> (-51.93%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#carryforward-flags-in-the-pull-request-comment) to find out more.

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[NoUmlautsAllowed]

Hi, thanks for your PR :) I will look into it the next days.

[qwerty287]

Done