feat: use openapigen v7.0.0

[t0mk]

This PR fixes openapigen docker image to tag v7.0.0.

It should fix pydantic to <2 and fix #46.
https://github.com/equinix-labs/metal-python/compare/openapigen_v7.0.0?expand=1#diff-f3eb11c13067f3b9839bc8411d47ce2d7d9c99c64478174609246bb88f41692cL4

also fixes #38

[ctreatma]

Are there new options we can set for the generator? It looks like there are a lot of potentially unnecessary or undesirable changes here; the docs seem to have been deleted entirely, and a bunch of *_api.py files have either been moved or deleted as well.

[t0mk]

@ctreatma Yes, the module seem to have changed :(. I need to check that python is indeed a sucessor of python-nextgen but if yes, it's not great that the generator changes module structure this much :(.

Docs moved:
https://github.com/equinix-labs/metal-python/blob/openapigen_v7.0.0/equinix_metal/docs/apis/tags/DevicesApi.md

There don't seem to be new params relevant to the changes:
https://openapi-generator.tech/docs/generators/python/
(unless they're uncdocumented)

I make this WIP

[t0mk]

@ctreatma, yesterday I accidentaly generated the code with the old-obsoleted python generator from the v6 openapigen, that's why the structure was so mangled.

The python generator is indeed sucessor of the experimental python-nextgen. I generated code with python generator from v7.0.0 now and the diff is leaner.

You can see Makefile updates in fe07e9b and the generated code update in 0fc266a

Please review

[ctreatma]

This looks way better! Thanks!