Several user fields can be null when signing with Idp

[druskus20]

Describe the bug
I am using part of this crate to sign in with an external identity provider (Github, in my case).

When trying to deserialize the authentication response to a firestore_db_and_auth::dto::OAuthResponse, I get the following error:

called `Result::unwrap()` on an `Err` value: RequestError(reqwest::Error { kind: Decode, source: Error("missing field `email`", line: 16, column: 1) })

The code I am running is below:

async fn sign_in_by_oauth2(
    api_key: &str,
    access_token: String,
    request_uri: String,
) -> Result<gcloud_sdk::Token, CoinError> {
    let uri = "https://identitytoolkit.googleapis.com/v1/accounts:signInWithIdp?key=".to_owned()
        + api_key;

    let post_body = format!("access_token={}&providerId={}", access_token, "github.com",);
    let return_idp_credential = true;
    let return_secure_token = true;

    let json = &SignInWithIdpRequest {
        post_body,
        request_uri,
        return_idp_credential,
        return_secure_token,
    };

    dbg!(&json);
    let response: Response = reqwest::Client::new().post(&uri).json(&json).send().await?;

    //dbg!(&response.text().await?);
    let oauth_response: OAuthResponse = response.json().await?; // breaks

    //dbg!(&oauth_response);

    todo!()
}

I can instead deserialize as .text() and see that the fields email, first_name and last_name happen to be null. (While all the other fields are correct). This suggests that the aforementioned OAuthResponse's fields field should be an Option<String>

The Google Cloud docs do not mention anything:

https://cloud.google.com/identity-platform/docs/reference/rest/v1/accounts/signInWithIdp