[Python] Added Support for Validating and Converting Model Attributes

[ckoegel]

Solves #11133

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[ckoegel]

Forcing the generator to throw errors when trying to create undeclared attributes caused many errors in the existing tests. I'm still fairly new to python, so I'm not sure if this is a widely accepted practice or not, but if anyone has insight as to why this is done and/or what should be done about it in this project, please let me know!

[ckoegel]

@spacether I noticed that a single test has failed. I don't believe this is related to the changes made in this PR, as the tests run when running ./mvnw clean package all pass and the build is successful. It seems as though there is a TypeError in the one test that fails. Is there an issue with something else that is known or is this most likely an unintended result of my changes?

[spacether]

@ckoegel more tests needed to be run. I just approved them. My intention is for users to not pass in spec named parameters into Model(args) like you are doing in this PR. Can you try what I suggested in your issue and respond there?

[spacether]

Please try using the different method that we have for using spec named inputs. If that works then this PR is not needed. If it does not work then we should fix that interface. Details are in the comment I left in your issue

[spacether]

As shown by comments in the ticket, spec property naming can be used by passing in the _spec_property_naming argument when instantiating models. We need that parameter to differentiate the two use cases where

• python named properties are input
• spec named properties are input

@ckoegel How about I close this PR because our code already supports Validating and Converting Model Attributes with python naming and spec naming?

[ckoegel]

PR has been updated to reflect the findings in #11133

[spacether]

Thank you for your PR. This looks great!

[spacether]

@ckoegel sorry for my delay on reviewing this PR. Could you regenerate the samples here?
CI shows that these files need to be updated:

	modified:   samples/openapi3/client/petstore/python/petstore_api/model/foo_object.py
	modified:   samples/server/petstore/python-aiohttp-srclayout/setup.py
	modified:   samples/server/petstore/python-aiohttp-srclayout/tests/conftest.py
	modified:   samples/server/petstore/python-aiohttp-srclayout/tox.ini

After that update is made I can merge it in.