Support of "Install Referrer API"

https://developer.android.com/google/play/installreferrer

Eg. Snikket is invite based, so the user gets an invite to join, a webpage (https://domain.tld/invite?TOKEN), with a button for the store that goes to: https://play.google.com/store/apps/details?id=app_id&referrer=xmpp%3Adomain.tld%3Fregister%3Bpreauth%3DTOKEN so when the user clicks it installs the app and the app is ready to go (asks the user for a nickname and sets a secure password so the user can register an account and chat) basically streamlining the whole onboarding process.

Other (xmpp client) apps that support this: Conversations (Snikket is based upon it of course), Pix-Art (yes a fork still), Conv6ations for Sum7 (guess lol) and Yaxim (version 0.9.9 which is not yet updated due to the unavailability of libs and FOSS flavour, but the dev is working on it).

Other apps? Dunno, maybe?

The Google API has a lot of "tracking" included (as expected right?) and back connections to Play, that we can just forgo.

There is a lib for this Kotlin/Java, but it's under the Android license afaics, so maybe the old broadcast method can be used (but devs would need to implement this separately for the foss flavour)