feat-add-files-from-qr (#8)

Reviewed-on: http://catelliub.zapto.org:3000/brontomark/flux/pulls/8
Co-authored-by: Mark M2 Macbook <marco@catelli.it>
Co-committed-by: Mark M2 Macbook <marco@catelli.it>

lib/core/utils/functions.dart

@@ -0,0 +1,9 @@
+// Funzione che chiede le chiavi a Supabase
+import 'package:get_it/get_it.dart';
+import 'package:supabase_flutter/supabase_flutter.dart';
+
+Future<String> getSignedUrl(String storagePath) async {
+  return await GetIt.I<SupabaseClient>().storage
+      .from('documents')
+      .createSignedUrl(storagePath, 60); // Link che si autodistrugge in 60s
+}