collected using form data (instead of JSON) and that it should have the specific
    fields `username` and `password`.

    All the initialization parameters are extracted from the request.

    The only difference between `OAuth2PasswordRequestFormStrict` and
    `OAuth2PasswordRequestForm` is that `OAuth2PasswordRequestFormStrict` requires the
    client to send the form field `grant_type` with the value `"password"`, which