Migrate to santhosh-tekuri/jsonschema

[yannh]

This migrates the JSON validation from https://github.com/xeipuuv/gojsonschema (unmaintained) to https://github.com/santhosh-tekuri/jsonschema . The "error messages with json-pointers to exact location" feature seems quite nice. It would be nice to also be able to solve xeipuuv/gojsonschema#322

Unit & Acceptance tests pass nicely but I've added a test for using the "non standalone" schemas (that contain HTTP references) and that currently fails. Tracking here santhosh-tekuri/jsonschema#102

While it would be a breaking change, Kubeconform uses the standalone files by default, and I am not sure if anyone uses the non-standalone schemas nor why someone would use those with Kubeconform, so I might release this as a breaking change, unless the feature gets implemented in jsonschema.

[yannh]

FYI @eyarz since I know you're using kubeconform quite a bit - this is swapping the kubeconform engine 🥳 tests pass fine (despite minor differences in error messages) and performance seems on par. Just a heads up if you can think of something that might break - so far it seems a perfectly good replacement. We'd be using a better maintained JSON schema validation lib, which might enable new features.

[yannh]

I wonder if they have interest in adding HTTP references https://github.com/santhosh-tekuri/jsonschema/blob/56baa8bb9ba78e8da42c113f788b8b17b2565f15/loader.go#L32

[eyarz]

@yannh thank you for the heads up!
we will also check it from our side and keep you posted if we will find something.

[yannh]

@eyarz I think this is good to merge now, passes all tests and additional tests I added. There might be slight differences in the output of errors. I won't make a new release just yet 👍

[eyarz]

yes, this change will break how we parse and view kubeconform output.
we pinned kubcomform go version so it will not break Datree CLI.