Support signInFlow: popup

[joakimbugge]

Hi!

Is it possible to set the sign-in flow to popup in v7 yet?

I'm hosting my app outside of Firebase and the redirect flow has never really worked... I'm happy to test v7, but this is unfortunately a showstopper.

[treefrog00]

In an SPA context a popup is easier to work with as well as being a bit less jarring for users. Even if technically it is possible to handle the redirect flow by storing all the required SPA state in local storage or the URL and resetting all state after redirect, it would be easier and cleaner if I could use a popup.