Support OpenAPI 3.1.x imports

[hobgoblina]

Did you search for existing issues already?
yes

Is your feature request related to a problem? Please describe.
I've got a large 3.1 spec that's too unwieldy to manually downgrade to 3.0 (and I haven't found a converter that does a half-decent job), and it's giving me errors when I try to import to slumber.

Describe the solution you'd like
Looks like the oas3 crate targets 3.1.x ... maybe an implementation with it can be added and then Slumber could look for the OpenAPI version to determine which package's implementation to use?

Describe alternatives you've considered
I've tried using various converters, both to OpenAPI 3.0 and Insomnia. Results have been unsalvageable.

[LucasPickering]

Sure, that library looks reasonably good. I can take a crack at this. Hopefully it will be pretty similar to the 3.0 implementation.

[LucasPickering]

I have a PR up to add this. It's blocked by a PR I had to make to oas3 though. Hopefully they merge that quickly and I can get this out soon.

[LucasPickering]

@hobgoblina In the mean time if you want to test this out you can install the dev version with:

cargo install --git https://github.com/LucasPickering/slumber --branch openapi-3.1 slumber

[hobgoblina]

sick, thanks for knocking this out so quick!!