consolidate Service interface and implementation classes

Oqtane.Client/Services/VisitorService.cs

@@ -10,6 +10,28 @@ using System.Globalization;
 
 namespace Oqtane.Services
 {
+    /// <summary>
+    /// Service to manage <see cref="Visitor"/>s on a <see cref="Site"/>
+    /// </summary>
+    public interface IVisitorService
+    {
+        /// <summary>
+        /// Get all <see cref="Visitor"/>s of this <see cref="Site"/>.
+        ///
+        /// </summary>
+        /// <param name="siteId">ID-reference of a <see cref="Site"/></param>
+        /// <returns></returns>
+        Task<List<Visitor>> GetVisitorsAsync(int siteId, DateTime fromDate);
+
+        /// <summary>
+        /// Get a specific <see cref="Visitor"/> of this <see cref="Site"/>.
+        ///
+        /// </summary>
+        /// <param name="visitorId">ID-reference of a <see cref="Visitor"/></param>
+        /// <returns></returns>
+        Task<Visitor> GetVisitorAsync(int visitorId);
+    }
+
     [PrivateApi("Don't show in the documentation, as everything should use the Interface")]
     public class VisitorService : ServiceBase, IVisitorService
     {