refactoring, enhancements, and some fixes

Oqtane.Client/Services/Interfaces/ISyncService.cs

@@ -0,0 +1,19 @@
+using Oqtane.Models;
+using System;
+using System.Threading.Tasks;
+
+namespace Oqtane.Services
+{
+    /// <summary>
+    /// Service to retrieve <see cref="Sync"/> information.
+    /// </summary>
+    public interface ISyncService
+    {
+        /// <summary>
+        /// Get sync events
+        /// </summary>
+        /// <param name="lastSyncDate"></param>
+        /// <returns></returns>
+        Task<Sync> GetSyncAsync(DateTime lastSyncDate);
+    }
+}