python-pydantic-v1: Handle response chartset in exception.

[igorgatis]

This PR fixes the issue #19862.

Currently, the generated code for python-pydantic-v1 tries to decode the response using utf-8. This fails when the response uses character sequence that is not utf-8, like so:

  File ".../.venv/lib/python3.11/site-packages/my_api/api_client.py", line 219, in __call_api
    e.body = e.body.decode('utf-8')
             ^^^^^^^^^^^^^^^^^^^^^^
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe7 in position 78: invalid continuation byte

This change tries to use charset from the response. It leaves content unchanged when decoding fails.

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[igorgatis]

@fa0311 @multani

[wing328]

thanks for the PR.

instead of using this, what about using the function that usually comes with the Python HTTP libraries instead, e.g. https://stackoverflow.com/questions/14592762/a-good-way-to-get-the-charset-encoding-of-an-http-response-in-python ?

(so that we don't need to reinvent the wheel and you may need to add another method in rest.py to return the charset)