feat: Support transient identities and traits

Author: khvn26

Diff for: lib/src/model/feature.g.dart

@@ -6,8 +6,12 @@ part 'identity.g.dart';
 /// Personalized user
 @JsonSerializable()
 class Identity {
+  @JsonKey(includeIfNull: false)
+  final bool? transient;
   final String identifier;
+
   const Identity({
+    this.transient,
     required this.identifier,
   });
 

Diff for: lib/src/model/flag.g.dart

@@ -8,13 +8,16 @@ part 'trait.g.dart';
 @JsonSerializable()
 class Trait {
   final int? id;
+  @JsonKey(includeIfNull: false)
+  final bool? transient;
   @JsonKey(name: 'trait_key')
   final String key;
   @JsonKey(name: 'trait_value', fromJson: _fromJson, toJson: _toJson)
   final dynamic value;
 
   Trait({
     this.id,
+    this.transient,
     required this.key,
     required this.value,
   });

Diff for: lib/src/model/flags_and_traits.g.dart

@@ -3,7 +3,7 @@ description: >-
   Core Package of Flutter Client SDK for https://www.flagsmith.com/, Flagsmith is 100% Open
   Source. Host yourself or let us take care of the hosting.
 
-version: 3.0.0
+version: 3.1.0
 homepage: https://github.com/Flagsmith/flagsmith-flutter-core
 repository: https://github.com/Flagsmith/flagsmith-flutter-core
 issue_tracker: https://github.com/Flagsmith/flagsmith-flutter-core/issues
@@ -14,13 +14,13 @@ environment:
 dependencies:
   crypto: ^3.0.1
   encrypt: ^5.0.1
-  rxdart: ^0.27.5
+  rxdart: ^0.28.0
   json_annotation: ^4.0.1
   collection: ^1.15.0
 dev_dependencies:
-  flutter_lints: ^1.0.0
-  test:  ">=1.16.0 <=1.17.12"
-  http_mock_adapter: ^0.3.2
+  flutter_lints: ^5.0.0
+  test: ^1.25.8
+  http_mock_adapter: ^0.6.1
   mockito: ^5.0.15
-  json_serializable: ^4.1.3
+  json_serializable: ^6.8.0
   build_runner: ^2.1.2