make event model const

packages/stream_chat/lib/src/models/event.dart

@@ -10,7 +10,7 @@ part 'event.g.dart';
 @JsonSerializable()
 class Event {
   /// Constructor used for json serialization
-  Event({
+  const Event({
     this.type,
     this.cid,
     this.connectionId,
@@ -27,16 +27,18 @@ class Event {
     this.channelId,
     this.channelType,
     this.parentId,
-    this.extraData,
-  }) : isLocal = true;
+    this.extraData = const {},
+    this.isLocal = true,
+  });
 
   /// Create a new instance from a json
-  factory Event.fromJson(Map<String, dynamic> json) =>
-      _$EventFromJson(Serialization.moveToExtraDataFromRoot(
-        json,
-        topLevelFields,
-      ))
-        ..isLocal = false;
+  factory Event.fromJson(Map<String, dynamic> json) => _$EventFromJson({
+        ...Serialization.moveToExtraDataFromRoot(
+          json,
+          topLevelFields,
+        ),
+        'is_local': false,
+      });
 
   /// The type of the event
   /// [EventType] contains some predefined constant types
@@ -89,11 +91,11 @@ class Event {
 
   /// True if the event is generated by this client
   @JsonKey(ignore: true)
-  bool isLocal;
+  final bool isLocal;
 
   /// Map of custom channel extraData
-  @JsonKey(includeIfNull: false)
-  final Map<String, dynamic>? extraData;
+  @JsonKey(defaultValue: {})
+  final Map<String, dynamic> extraData;
 
   /// Known top level fields.
   /// Useful for [Serialization] methods.
@@ -114,7 +116,6 @@ class Event {
     'channel_id',
     'channel_type',
     'parent_id',
-    'is_local',
   ];
 
   /// Serialize to json