switch secrets to loading from env - towards a more unified way of handling secrets

frontend/ios/Runner/AppDelegate.swift

@@ -1,5 +1,6 @@
 import UIKit
 import Flutter
+import GoogleMaps
 
 @main
 @objc class AppDelegate: FlutterAppDelegate {
@@ -7,6 +8,9 @@ import Flutter
     _ application: UIApplication,
     didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
   ) -> Bool {
+    // load the key from env
+    let key = ProcessInfo.processInfo.environment["GOOGLE_MAPS_API_KEY"]!
+    GMSServices.provideAPI(key)
     GeneratedPluginRegistrant.register(with: self)
     return super.application(application, didFinishLaunchingWithOptions: launchOptions)
   }