gameInviteLink function
Returns a shareable invite link for the given join code, or null if
appHost is not configured.
Produces a URL such as https://strategy.eigeninteractive.com/join/ABC123
that opens the app directly on devices where it is installed, or shows
the fallback landing page otherwise.
appHost comes from EngineConfig.appHost and must match the domain
declared in AndroidManifest.xml and Runner.entitlements.
Implementation
Uri? gameInviteLink(String code, {required String? appHost}) =>
appHost != null ? Uri.https(appHost, '/join/$code') : null;