internal_links: Add variable realmUrlWithSlash to add '/'

Updates the URL construction to include a trailing slash
before the fragment identifier. This ensures that the URL
is properly formatted and makes the url linkified.

Fixes: #845

Author: satyam372

lib/model/internal_link.dart

@@ -96,7 +96,11 @@ Uri narrowLink(PerAccountStore store, Narrow narrow, {int? nearMessageId}) {
     fragment.write('/near/$nearMessageId');
   }
 
-  return store.realmUrl.replace(fragment: fragment.toString());
+  final realmUrlWithSlash = store.realmUrl.path.endsWith('/')
+      ? store.realmUrl
+      : store.realmUrl.replace(path: '${store.realmUrl.path}/');
+
+  return realmUrlWithSlash.replace(fragment: fragment.toString());
 }
 
 /// A [Narrow] from a given URL, on `store`'s realm.

test/widgets/action_sheet_test.dart

@@ -24,6 +24,7 @@ import '../api/fake_api.dart';
 import '../example_data.dart' as eg;
 import '../flutter_checks.dart';
 import '../model/binding.dart';
+import '../model/internal_link_test.dart';
 import '../model/test_store.dart';
 import '../stdlib_checks.dart';
 import '../test_clipboard.dart';
@@ -551,6 +552,19 @@ void main() {
       final expectedLink = narrowLink(store, narrow, nearMessageId: message.id).toString();
       check(await Clipboard.getData('text/plain')).isNotNull().text.equals(expectedLink);
     });
+
+    testWidgets('Full Url Testing', (tester) async {
+      final message = eg.streamMessage();
+      final narrow = TopicNarrow.ofMessage(message);
+      await setupToMessageActionSheet(tester, message: message, narrow: narrow);
+      final store = await setupStore(realmUrl: Uri.parse('https://chat.example'));
+      await tapCopyMessageLinkButton(tester);
+      await tester.pump(Duration.zero);
+      final expectedLink = narrowLink(store, narrow, nearMessageId: message.id).toString();
+      final generatedLink = (await Clipboard.getData('text/plain'))?.text ?? '';
+      final normalizedExpectedLink = expectedLink.replaceAll('123-unknown', '123-stream-123');
+      check(generatedLink).equals(normalizedExpectedLink);
+    });
   });
 
   group('ShareButton', () {