Added pagination and search logic in space tree

lib/pages/space_tree/model/pagination_model.dart

@@ -0,0 +1,20 @@
+import 'package:syncrow_web/pages/spaces_management/all_spaces/model/community_model.dart';
+
+class PaginationModel {
+  final int pageNum;
+  final bool hasNext;
+  final int size;
+  final List<CommunityModel> communities;
+
+  const PaginationModel(
+      {required this.pageNum,
+      required this.hasNext,
+      required this.size,
+      required this.communities});
+
+  const PaginationModel.emptyConstructor()
+      : pageNum = 1,
+        hasNext = true,
+        size = 10,
+        communities = const [];
+}