TF-3712 Add SettingsCapability to hide language setting

server_settings/lib/server_settings/capability_server_settings.dart

@@ -1,3 +1,26 @@
 import 'package:jmap_dart_client/jmap/core/capability/capability_identifier.dart';
+import 'package:jmap_dart_client/jmap/core/capability/capability_properties.dart';
+import 'package:json_annotation/json_annotation.dart';
 
-final capabilityServerSettings = CapabilityIdentifier(Uri.parse('com:linagora:params:jmap:settings'));
+part 'capability_server_settings.g.dart';
+
+final capabilityServerSettings = CapabilityIdentifier(Uri.parse('com:linagora:params:jmap:settings'));
+
+@JsonSerializable()
+class SettingsCapability extends CapabilityProperties {
+  SettingsCapability({this.readOnlyProperties});
+
+  final List<String>? readOnlyProperties;
+
+  factory SettingsCapability.fromJson(Map<String, dynamic> json) =>
+      _$SettingsCapabilityFromJson(json);
+
+  Map<String, dynamic> toJson() => _$SettingsCapabilityToJson(this);
+
+  factory SettingsCapability.deserialize(Map<String, dynamic> json) {
+    return SettingsCapability.fromJson(json);
+  }
+  
+  @override
+  List<Object?> get props => [readOnlyProperties];
+}