fix: correctly derive a valid JSON Schema from an OAS parameter

[XVincentX]

This PR updates Graphite in Prism to use the latest version which includes the JSON Schema normalisation features.

1. Update packages (Typescript, Types, Graphite)
2. Cleaned up the examples from optional properties. In the new graphite a lot of fields are not mandatory and this requires an additional round of checks in Prism. An example is here
3. The new graphite pointed out some inconsistencies in the previous handmade validator — which are now fixed since it has been offloaded to Ajv
4. Added a specific test to make sure the validator is not case sensitive (headers) — comically speaking, this worm hole started from this specific issue

P.S: There are some other weird things happening in the deserialisation that I want to lookup and fix, but not here, not now.

Closes #324

[chris-miaskowski]

Hey @XVincentX, great job so far! Left you a bunch of smaller comments.
My last point is that I couldn't find a test case for the originally reported issue (the header param).
Maybe we could take the exact spec provided in the original issue report and use it to feed the test?

[XVincentX]

@philsturgeon @chris-miaskowski

Please have another look.

[XVincentX]

My last point is that I couldn't find a test case for the originally reported issue (the header param).
Maybe we could take the exact spec provided in the original issue report and use it to feed the test?

Can you elaborate more? What is the test that's missing? The original issue was on the camel case of the headers, which now have a test.

[philsturgeon]

@XVincentX what I meant about the tests, is that we should probably add some cases to the functional tests for changes as we go. packages/http/src/mocker/tests/functional.spec.ts didnt seem to get any love?

[XVincentX]

@philsturgeon That test file is testing the mocker, which is after the validation step. I understand what you mean though, I'll find the relevant file and add the stuff you asked for.