[PYTHON] generate code based on pydantic v2

[fa0311]

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package 
  ./bin/generate-samples.sh ./bin/configs/*.yaml
  ./bin/utils/export_docs_generators.sh
  

  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
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[fa0311]

It is not wise to include the document url in the test
Since pydantic v2.4.0 was released a few hours ago, the URL has changed and the test will fail

[wing328]

agreed. we didn't take into consideration upgrading pydantic to newer version when writing the test. please feel free to revise the test

[fa0311]

should use .model_rebuild(raise_errors=False) instead of try.
However, this is a stopgap measure and in practice should be implemented without using raise_errors.
I spent a lot of time trying to rebuild without raise_errors, but couldn't come up with a good solution.

[wing328]

I think we can remove the usePydanticV2 switch the template and the java class as python client generator now only supports pydantic v2.

[jakubno]

I didn't use the usePydanticV2 flag 🙈

I've tested it and found following issues:

• The code doesn't work for models with camel case names:

class Session(BaseModel):
    """
    Session
    """
session_id: StrictStr = Field(
        ..., alias="sessionID", description="Identifier of the session"
    )

then I am receiving following error:

pydantic_core._pydantic_core.ValidationError: 1 validation errors for Session
 sessionID
   Field required [type=missing, input_value={'session_id': 'fce131d5'}, input_type=dict]
     For further information visit https://errors.pydantic.dev/2.4/v/missing

• parse_obj - is still in some places
• there's still @validate_arguments in the code:

PydanticDeprecatedSince20: The `validate_arguments` method is deprecated; use `validate_call` instead. Deprecated in Pydantic V2.0 to be removed in V3.0. See Pydantic V2 Migration Guide at https://errors.pydantic.dev/2.4/migration/
    @validate_arguments

Python version: 3.11.5
Pydantic: 2.4.0

[fa0311]

Continue to #16685