Function auth 

pub async fn auth(
    cache_key: &str,
    opts: AuthOpts<'_>,
) -> Result<AuthResult, AuthError>

Authenticate with Microsoft. If the data isn’t cached, the user will be asked to go to log into Microsoft in a web page.

The cache key is an arbitrary string that’s used to identify the account in the future. The account email is often used for this.

If you want to use your own code to cache or show the auth code to the user in a different way, use get_ms_link_code, get_ms_auth_token, get_minecraft_token and get_profile instead.