initial_snapshot: Accept unknown "emojiset" values

Fixes #1981.

Author: MritunjayTiwari14

lib/api/model/initial_snapshot.dart

@@ -295,6 +295,7 @@ class UserSettings {
   TwentyFourHourTimeMode twentyFourHourTime;
 
   bool displayEmojiReactionUsers;
+  @JsonKey(unknownEnumValue: Emojiset.unknown)
   Emojiset emojiset;
   bool presenceEnabled;
 

lib/api/model/initial_snapshot.g.dart

@@ -390,7 +390,8 @@ enum Emojiset {
   google,
   googleBlob,
   twitter,
-  text;
+  text,
+  unknown;
 
   /// Get an [Emojiset] from a raw string. Throws if the string is unrecognized.
   ///

lib/api/model/model.dart

@@ -3,6 +3,7 @@ import 'package:test/scaffolding.dart';
 import 'package:zulip/api/model/initial_snapshot.dart';
 import 'package:zulip/api/model/model.dart';
 
+import '../../example_data.dart' as eg;
 import '../../stdlib_checks.dart';
 
 void main() {
@@ -62,4 +63,15 @@ void main() {
       'unread_message_ids': [11, 2, 3],
     })).throws<AssertionError>();
   });
+
+  test('UserSettings.emojiset handles various unknown values', () {
+    final unknownValues = ['apple', 'microsoft', 'facebook', ''];
+    for (final unknownValue in unknownValues) {
+      final json = eg.userSettings().toJson()..['emojiset'] = unknownValue;
+      final settings = UserSettings.fromJson(json);
+
+      // Verify unknown emojiset defaults to Emojiset.unknown
+      check(settings.emojiset).equals(Emojiset.unknown);
+    }
+  });
 }

lib/api/model/model.g.dart

@@ -1304,6 +1304,20 @@ const _globalStore = globalStore;
 
 const String defaultRealmEmptyTopicDisplayName = 'test general chat';
 
+UserSettings userSettings({
+  TwentyFourHourTimeMode? twentyFourHourTime,
+  bool? displayEmojiReactionUsers,
+  Emojiset? emojiset,
+  bool? presenceEnabled,
+}) {
+  return UserSettings(
+    twentyFourHourTime: twentyFourHourTime ?? TwentyFourHourTimeMode.twentyFourHour,
+    displayEmojiReactionUsers: displayEmojiReactionUsers ?? true,
+    emojiset: emojiset ?? Emojiset.unknown ,
+    presenceEnabled: presenceEnabled ?? true,
+  );
+}
+
 InitialSnapshot initialSnapshot({
   String? queueId,
   int? lastEventId,