Add support for OpenAPI 3

[mristin]

It should be fairly feasible to add support for OpenAPI 3 as swagger-to uses an intermediate layer. While we couldn't support all the features of OpenAPI 3, we could at least covert the overlap in features between Swagger (OpenAPI 2) and OpenAPI 3.

@falzm I suppose you would be interested in this feature? I would need a bit of help. While I can do the coding, I would need somebody to review the code (at least skim over it) and help me convert the specs in the unit tests from Swagger to OpenAPI 3. Would you have time and energy for that in the foreseeable future? I don't expect the effort to be huge.

[falzm]

Hi @mristin, you can count on me for testing your implementation against an actual OpenAPI 3 spec.

[mristin]

Hi @falzm and possibly others,
I had another look at https://github.com/OpenAPITools/openapi-generator -- it seems like it went a long way from swagger-gen. Before I spend many hours trying to get the OpenAPI3 model into python, could you maybe outline why you'd prefer to use swagger-to instead of openapi-generator? Are the stubs/clients from swagger-to better and if so, in which way(s)?

[mristin]

I am actually thinking to create first a good openapi3 python library, on top of which we can stack other tools (generators, validators etc.). The main benefit of such a library would be that we could use Python (elegant) instead of Java (clumsy).

@falzm what do you think?

[mristin]

@Alle123 maybe you also have some thoughts on this matter?