TF-4169 Create Labels capability and Label object

labels/lib/converter/hex_color_nullable_converter.dart

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+import 'package:json_annotation/json_annotation.dart';
+import 'package:labels/model/hex_color.dart';
+
+class HexColorNullableConverter implements JsonConverter<HexColor?, String?> {
+  const HexColorNullableConverter();
+
+  @override
+  HexColor? fromJson(String? json) => json != null ? HexColor(json) : null;
+
+  @override
+  String? toJson(HexColor? object) => object?.value;
+}

labels/lib/labels.dart

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+export 'package:labels/model/label.dart';
+export 'package:labels/model/hex_color.dart';
+
+export 'package:labels/utils/labels_constants.dart';

labels/lib/model/hex_color.dart

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+import 'package:equatable/equatable.dart';
+
+class HexColor with EquatableMixin {
+  final String value;
+
+  HexColor(this.value);
+
+  @override
+  List<Object> get props => [value];
+}

labels/lib/model/label.dart

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+import 'package:equatable/equatable.dart';
+import 'package:jmap_dart_client/http/converter/id_converter.dart';
+import 'package:jmap_dart_client/jmap/core/id.dart';
+import 'package:json_annotation/json_annotation.dart';
+import 'package:labels/converter/hex_color_nullable_converter.dart';
+import 'package:labels/model/hex_color.dart';
+
+part 'label.g.dart';
+
+@JsonSerializable(
+  explicitToJson: true,
+  includeIfNull: false,
+  converters: [
+    IdConverter(),
+    HexColorNullableConverter(),
+  ],
+)
+class Label with EquatableMixin {
+  final Id id;
+  final String displayName;
+  final String keyword;
+  final HexColor? color;
+
+  Label(this.id, this.displayName, this.keyword, this.color);
+
+  factory Label.fromJson(Map<String, dynamic> json) => _$LabelFromJson(json);
+
+  Map<String, dynamic> toJson() => _$LabelToJson(this);
+
+  @override
+  List<Object?> get props => [
+        id,
+        displayName,
+        keyword,
+        color,
+      ];
+}

labels/lib/utils/labels_constants.dart

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+import 'package:jmap_dart_client/jmap/core/capability/capability_identifier.dart';
+
+class LabelsConstants {
+  LabelsConstants._();
+
+  static final CapabilityIdentifier labelsCapability =
+      CapabilityIdentifier(Uri.parse('com:linagora:params:jmap:labels'));
+}