Show space hierarchies

Fixes #83

lib/models/requests/get_space_hierarchy.dart

@@ -0,0 +1,19 @@
+import "package:freezed_annotation/freezed_annotation.dart";
+
+part "get_space_hierarchy.freezed.dart";
+part "get_space_hierarchy.g.dart";
+
+@Freezed(toJson: false, fromJson: false)
+@JsonSerializable(includeIfNull: false)
+class const GetSpaceHierarchyRequest({
+  required final String roomId,
+  final String? from,
+  final int limit = 50,
+  final int? maxDepth,
+  final bool? suggestedOnly,
+}) with _$GetSpaceHierarchyRequest {
+  Map<String, Object?> toJson() => _$GetSpaceHierarchyRequestToJson(this);
+
+  factory GetSpaceHierarchyRequest.fromJson(Map<String, Object?> json) =>
+      _$GetSpaceHierarchyRequestFromJson(json);
+}