fix: add snippet for old android (with no lets encrypt certificate)

assets/lets-encrypt-r3.pem

@@ -0,0 +1,30 @@
+-----BEGIN CERTIFICATE-----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+FHm0WeZ7tuXkAXOACIjIGlj26ZtuMDIGCCsGAQUFBwEBBCYwJDAiBggrBgEFBQcw
+AoYWaHR0cDovL3gxLmkubGVuY3Iub3JnLzAnBgNVHR8EIDAeMBygGqAYhhZodHRw
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+gt8TAQEBMA0GCSqGSIb3DQEBCwUAA4ICAQCFyk5HPqP3hUSFvNVneLKYY611TR6W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+-----END CERTIFICATE-----

lib/main.dart

@@ -1,6 +1,9 @@
 import 'dart:async';
+import 'dart:io';
 import 'dart:math';
 
+import 'package:flutter/services.dart';
+import 'package:http/http.dart' as http;
 import 'package:flarte/helpers.dart';
 import 'package:flarte/config.dart';
 import 'package:flutter/foundation.dart';
@@ -24,6 +27,21 @@ void main() async {
     debugPrint = (String? message, {int? wrapWidth}) {};
   }
 
+  try {
+    // check we can reach some let's encrypt certificate based website
+    final http.Response _ =
+        await http.get(Uri.parse('https://valid-isrgrootx1.letsencrypt.org/'));
+  } on HandshakeException {
+    // load Let's Encrypt new certificate if this has failed
+    ByteData data =
+        await PlatformAssetBundle().load('assets/lets-encrypt-r3.pem');
+    SecurityContext.defaultContext
+        .setTrustedCertificatesBytes(data.buffer.asUint8List());
+  } on SocketException {
+    // TODO: we need to recheck that later on
+    debugPrint('debug: Failed to test for valid-isrgrootx1.letsencrypt.org');
+  }
+
   final SharedPreferences prefs = await SharedPreferences.getInstance();
   AppConfig.textMode = prefs.getBool('textMode') ?? AppConfig.textMode;
   AppConfig.dlDirectory = prefs.getString('dlDirectory') ?? '';

pubspec.yaml

@@ -85,6 +85,7 @@ flutter:
   assets:
     - assets/flarte.png
     - assets/GPL3.txt
+    - assets/lets-encrypt-r3.pem
 
   # An image asset can refer to one or more resolution-specific "variants", see
   # https://flutter.dev/assets-and-images/#resolution-aware