Update spec to OpenAPI 3.0.1

[clarakosi]

• swagger: 2.0 has been replaced with openapi: 3.0.1
• definitions was renamed to schemas and  securityDefinitions to securitySchemes and they all were moved inside components
• servers replaces the basePath  keywords used in OpenAPI 2.0

Bug: T218218

[coveralls]

Coverage increased (+0.1%) to 91.529% when pulling 08368d0 on clarakosi:swagger into f974df2 on wikimedia:master.

[coveralls]

Coverage increased (+0.1%) to 91.529% when pulling 08368d0 on clarakosi:swagger into f974df2 on wikimedia:master.

[coveralls]

Coverage increased (+0.1%) to 91.513% when pulling 70505ab on clarakosi:swagger into f974df2 on wikimedia:master.

[d00rman]

I think it would better if we kept compatibility with swagger v2 at least for now, it will make the transition much easier. Other minor comments in-lined.

[Pchelolo]

The validator was not only responsible for validating the parameters, it's also responcible for casting the incoming parameters to right types. I believe the logic there with _paramCoersionFun and _bodyCoersionFun was dependent on swagger 2, so it now doesn't work. This is why, for example, you needed to JSON.parse some stuff manually here https://github.com/wikimedia/restbase/pull/1120/files#diff-d91965930eda1e26c9b5db0d3041c4acR590

[Pchelolo]

The tests for the validator should also be updated even more, some of the specs in the tests use outdated stuff, for example 'formData'

[Pchelolo]

Let's, for now, remove node from travis.yaml - node 12 has been released recently and getting support for a new major node version is unrelated to this work. We should also file a ticket for node 12 support and do it separately. I've checked and the tests fail locally with node 12 even without this pull request, so it's clearly something else.

[Pchelolo]

The name 'requestBody' is a little confusing. It's the req body spec, not the body itself right? Can we make it less confusing?

[Pchelolo]

So, here we assume that only 'schemas' out of components will be used in parameter definitions (like we do now in RESTBase) for example. Starting to use parameters components seem nice, we have a lot of shared parameters like title or accept between endpoitns, so abstracting that out would be neat. However, these 2 PRs are already enormous, so we can followup to do that in the next iteration. For now, would you mind adding a comment that that is not supported?

[clarakosi]

IDK requestBody is what is used in the swagger docs and spec so it seems appropriate to follow that name.

I did make a note that parameters and requestBodies are not currently supported in components.

[Pchelolo]

Almost there! Left a couple of comments, but overall LGTM

[clarakosi]

Published as v0.12.0