Support for OpenAPI 3.0

[ezoerner]

Support for OpenAPI 3.0.x (current version is 3.0.2).
Surprisingly, I don't see an issue for this yet, seeing as how 3.0.0 has been out since 2017-07-26.

[phadej]

There are no library for OpenAPI 3.0. If someone makes it happen, then servant-openapi3 is easy to do. See GetShopTV/swagger2#105

[cies]

This seems to come up a lot for openapi3 servant searches. There seems to be some good news:

https://github.com/fieldstrength/servant-openapi/tree/master/openapi

Enjoy.

[andys8]

And https://github.com/biocad/servant-openapi3