store related events for mentions

lib/models/mentions_response.dart

@@ -0,0 +1,16 @@
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:freezed_annotation/freezed_annotation.dart";
+import "package:nexus/models/event.dart";
+
+part "mentions_response.freezed.dart";
+part "mentions_response.g.dart";
+
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable(createToJson: false)
+class const MentionsResponse({
+  required final IList<Event> events,
+  final IList<Event> relatedEvents = const .empty(),
+}) with _$MentionsResponse {
+  factory MentionsResponse.fromJson(Map<String, Object?> json) =>
+      _$MentionsResponseFromJson(json);
+}