relocate folder hierarchy logic to folder repository (consistent with page approach)

Oqtane.Server/Repository/FolderRepository.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using Microsoft.AspNetCore.Hosting;
@@ -45,7 +46,49 @@ namespace Oqtane.Repository
             {
                 folder.PermissionList = permissions.Where(item => item.EntityId == folder.FolderId).ToList();
             }
-            return folders;
+            return GetFoldersHierarchy(folders);
+        }
+
+        private static List<Folder> GetFoldersHierarchy(List<Folder> folders)
+        {
+            List<Folder> hierarchy = new List<Folder>();
+            Action<List<Folder>, Folder> getPath = null;
+            getPath = (folderList, folder) =>
+            {
+                IEnumerable<Folder> children;
+                int level;
+                if (folder == null)
+                {
+                    level = -1;
+                    children = folders.Where(item => item.ParentId == null);
+                }
+                else
+                {
+                    level = folder.Level;
+                    children = folders.Where(item => item.ParentId == folder.FolderId);
+                }
+
+                foreach (Folder child in children)
+                {
+                    child.Level = level + 1;
+                    child.HasChildren = folders.Any(item => item.ParentId == child.FolderId);
+                    hierarchy.Add(child);
+                    getPath(folderList, child);
+                }
+            };
+            folders = folders.OrderBy(item => item.Name).ToList();
+            getPath(folders, null);
+
+            // add any non-hierarchical items to the end of the list
+            foreach (Folder folder in folders)
+            {
+                if (hierarchy.Find(item => item.FolderId == folder.FolderId) == null)
+                {
+                    hierarchy.Add(folder);
+                }
+            }
+
+            return hierarchy;
         }
 
         public Folder AddFolder(Folder folder)