[BUG][python] string format password throws AttributeError: 'SecretStr' object has no attribute 'to_dict'

Bug Report Checklist

• [x ] Have you provided a full/minimal spec to reproduce the issue?
• [ x] Have you validated the input using an OpenAPI validator (example)?
• [ x] Have you tested with the latest master to confirm the issue still exists?
• [ x] Have you searched for related issues/PRs?
• [ x] What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Calling a method with a credential object holding a password attribute of type string with format: password fails in the generated Python client code.

openapi-generator version

I tested this on the current v7.0.0-beta as well as with todays trunk using the python (was python-nextgen) generator.

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  title: ""
  version: ""
paths:
  /accounts/users/authenticate:
    post:
      operationId: authenticate
      summary: Authenticate user
      description: Authenticates user and returns bearer token
      tags:
        - account
      security: []
      requestBody:
        description: User credentials
        required: true
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/Credentials"
      responses:
        200:
            description: OK
components:
  schemas:
    Credentials:
      type: object
      properties:
        email:
          type: string
          description: email address
          example: me@work.com
        password:
          type: string
          format: password
          description: password
          example: secret
      required:
        - email
        - password

Generation Details

java -jar openapi-generator-cli/target/openapi-generator-cli.jar generate -i openapi-schema.yaml -g python

Steps to reproduce

import time
import os
import openapi_client
from openapi_client.rest import ApiException
from pprint import pprint

configuration = openapi_client.Configuration(
    host = "http://localhost"
)

with openapi_client.ApiClient(configuration) as api_client:
    api_instance = openapi_client.AccountApi(api_client)
    credentials = openapi_client.Credentials(email="me@email.com", password="123")
    api_response = api_instance.authenticate(credentials)

fails with

Traceback (most recent call last):
  File "<stdin>", line 5, in <module>
  File "pydantic/decorator.py", line 40, in pydantic.decorator.validate_arguments.validate.wrapper_function
  File "pydantic/decorator.py", line 134, in pydantic.decorator.ValidatedFunction.call
  File "pydantic/decorator.py", line 206, in pydantic.decorator.ValidatedFunction.execute
  File "./openapi_client/api/account_api.py", line 73, in authenticate
    return self.authenticate_with_http_info(credentials, **kwargs)  # noqa: E501
[ cut ]
  File "./openapi_client/api_client.py", line 291, in sanitize_for_serialization
    obj_dict = obj.to_dict()
               ^^^^^^^^^^^
AttributeError: 'SecretStr' object has no attribute 'to_dict'

Generate the Python client from the OpenAPI declaration and reproduce the failure with Credentials in the generated account_api.py. Start in api_client.py at sanitize_for_serialization and inspect how the generated password field is represented; done means the authenticate call serializes the credentials without the SecretStr AttributeError.