Method to retrieve the OAuth URL or opening the URL in the browser using the open crate

[johaan22]

It would be very useful to implement a method to retrieve the URL from the InstalledFlowAuthenticator. If there is already a way of doing this, it would be awesome to show an example in the documentation.

The main benefit of retrieving the URL is that I can use the open crate to open the URL using my default browser rather than have it print in the console, or, a method can be added to the crate to make this feature more native.

[dermesser]

Can you open the browser from a flow delegate? https://docs.rs/yup-oauth2/latest/yup_oauth2/authenticator/struct.AuthenticatorBuilder.html#impl-AuthenticatorBuilder%3CC,+InstalledFlow%3E