Flow.autogenerate_code_verifier does not default to True and flow.code_verifier is None

[kosperun]

Environment details

• OS type and version: OSX Sonoma 14.5
• Python version: python --versionPython 3.11.4
• pip version: pip --version 23.1.2
• google-auth-oauthlib version: pip show google-auth-oauthlib 1.1.0

Steps to reproduce

1. Create an instance of Flow from client config:
2. Generate an authorization url from Flow instance
3. Try to access code_verifier and it will be None

Code example

client_config = {
        "web": {
                "client_id": YOUR_CLIENT_ID,
                "client_secret": YOUR_CLIENT_SECRET,
                "auth_uri": "https://accounts.google.com/o/oauth2/auth",
                "token_uri": "https://oauth2.googleapis.com/token",
                "redirect_uris": [redirect_uri],
            }
        }

flow = Flow.from_client_config(
            client_config,
            scopes=scopes,
            redirect_uri=redirect_uri)

url, gen_state = flow.authorization_url(prompt="consent select_account", state=state)

>>>flow.code_verifier is None
>>>True

Stack trace

# example

Making sure to follow these steps will guarantee the quickest resolution possible.

Thanks!