Drop openapi-spec-validator for custom ref handler

[RobbeSneyders]

Fixes #930
Continues on #936

This PR completely removes the dependency on openapi-spec-validator. There's multiple reasons to do this:

• One dependency less
• We don't use openapi-spec-validator for it's main purpose, but for utility functionality
• It's not production ready (Version 0.2.0 introduces breaking change due to version upgrade python-openapi/openapi-schema-validator#31 (comment))
• We recently had some issues with dependency conflicts (Support jsonschema >= 4.0.0 #1430 (comment))

[coveralls]

Pull Request Test Coverage Report for Build 1877457959

• 20 of 31 (64.52%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.3%) to 96.744%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
connexion/json_schema.py	20	31	64.52%

Totals
Change from base Build 1877449835:	-0.3%
Covered Lines:	2882
Relevant Lines:	2979

---

💛 - Coveralls

[Ruwann]

Thanks, Robbe! Think we just need to adjust the tests for this?

[Ruwann]

Why do we need to do this? Shouldn't the loaded file be json as well if it adheres to OpenAPI? Perhaps I'm simply overlooking something.

[RobbeSneyders]

The loaded file can be a yaml file as well, which allows integer keys. According to the OpenAPI spec, keys should indeed be strings so the yaml is a representation of valid json, and we shouldn't need this. However openapi-spec-validator allowed this, and I tried to provide a drop-in replacement so kept the same behavior.

We could mark this for deprecation in the next major version though.

[Ruwann]

Can we add a separate test for this and change this back to the original value?

[RobbeSneyders]

Woops, this is leftover from my local testing.
I'll remove this and add a separate test.
Strange that this doesn't fail in the Github pipeline though.

[RobbeSneyders]

Ok, so this didn't break because this is an example, not a test 😅

It's unfortunately not straightforward to add a test, sine only absolute paths are supported (#254). So I would propose to merge without unless you have an idea on how to do it?

[Ruwann]

Agreed, I don't see a good way of adding a test for this, so I would merge without it.