iOS: Support auth

[binwiederhier]

[binwiederhier]

I've begun work on this here: binwiederhier/ntfy-ios#6

Screenshots in Discord

[binwiederhier]

This is done

[ozpinu]

This is fantastic - will a new version of the app be pushed to the app store/test flight to test this?

[binwiederhier]

I have a bunch of other things in the milestone (https://github.com/binwiederhier/ntfy/milestone/1), nad I was gonna see if I can at least do some of them before doing another TestFlight release. Couple of days