Pydantic v1/2 compatibility

[webb-ben]

Overview

This PR backports Pydantic v1 compatibility to better allow long term package management.

Related Issue / discussion

#1766
#1664
#1573

Additional information

Dependency policy (RFC2)

• I have ensured that this PR meets RFC2 requirements

Updates to public demo

• I have ensured that breaking changes to the pygeoapi master demo server have been addressed
  • https://github.com/geopython/demo.pygeoapi.io/blob/master/services/pygeoapi_master/local.config.yml

Contributions and licensing

(as per https://github.com/geopython/pygeoapi/blob/master/CONTRIBUTING.md#contributions-and-licensing)

• I'd like to contribute [feature X|bugfix Y|docs|something else] to pygeoapi. I confirm that my contributions to pygeoapi will be compatible with the pygeoapi license guidelines at the time of contribution
• I have already previously agreed to the pygeoapi Contributions and Licensing Guidelines

[kalxas]

Thank you @webb-ben for this contribution!
This PR unblocks usage/packaging of pydantic 1.x in some production environments.

[francbartoli]

I'd like to make you aware that

class OAPIFormat(BaseModel):
    root: SupportedFormats = SupportedFormats.YAML

will break for example

Also, how are we imaging to handle packaging in the long term and support at the same time v1 and v2 within the same Dockerfile?

@kalxas I had understood the plan, according to this was to avoid this controversial situation on master and support production deployments with the stable branch

[kalxas]

@francbartoli yes, that was the plan but unfortunately nothing has yet been ported to the stable branch.
If we could support both pydantic versions it would be easier to release from master.
No changes are expected for Dockerfile, it would remain as is (pydantic 2.x)

Another option is keep this PR just for the stable branch.

Regarding the breakage you point to, should we add some test to be able to detect?

[GeoSander]

Wow, I haven't checked in on the project for a while 😅
Don't know when this was introduced, but I am happy to see that Pydantic is now being used in pygeoapi! 👍