fix: copy link to block not supported well

Author: asjqkkkk

frontend/appflowy_flutter/integration_test/desktop/document/document_copy_and_paste_test.dart

@@ -483,16 +483,6 @@ void main() {
       });
     });
 
-    testWidgets('paste image url without extension', (tester) async {
-      const plainText =
-          'https://images.unsplash.com/photo-1469474968028-56623f02e42e?ixlib=rb-4.0.3&q=85&fm=jpg&crop=entropy&cs=srgb&dl=david-marcu-78A265wPiO4-unsplash.jpg&w=640';
-      await tester.pasteContent(plainText: plainText, (editorState) {
-        final node = editorState.getNodeAtPath([0])!;
-        expect(node.type, ImageBlockKeys.type);
-        expect(node.attributes[ImageBlockKeys.url], isNotEmpty);
-      });
-    });
-
     const testMarkdownText = '''
 # I'm h1
 ## I'm h2

frontend/appflowy_flutter/lib/plugins/document/presentation/editor_plugins/delta/text_delta_extension.dart

@@ -1,3 +1,4 @@
+import 'package:appflowy/plugins/document/presentation/editor_plugins/link_preview/custom_link_parser.dart';
 import 'package:appflowy/plugins/document/presentation/editor_plugins/mention/mention_block.dart';
 import 'package:appflowy_editor/appflowy_editor.dart';
 
@@ -27,9 +28,15 @@ extension TextDeltaExtension on Delta {
         if (op.text == MentionBlockKeys.mentionChar) {
           final mention = attributes?[MentionBlockKeys.mention];
           final mentionPageId = mention?[MentionBlockKeys.pageId];
+          final mentionType = mention?[MentionBlockKeys.type];
           if (mentionPageId != null) {
             text += await getMentionPageName(mentionPageId);
             continue;
+          } else if (mentionType == MentionType.externalLink.name) {
+            final url = mention?[MentionBlockKeys.url] ?? '';
+            final info = await LinkInfoCache().get(url);
+            text += info?.siteName ?? url;
+            continue;
           }
         }