consolidate Service interface and implementation classes

Oqtane.Client/Services/OutputCacheService.cs

@@ -1,12 +1,23 @@
 using System.Net.Http;
-using System.Threading;
 using System.Threading.Tasks;
-
 using Oqtane.Documentation;
 using Oqtane.Shared;
 
 namespace Oqtane.Services
 {
+    /// <summary>
+    /// Service to manage cache
+    /// </summary>
+    public interface IOutputCacheService
+    {
+        /// <summary>
+        /// Evicts the output cache for a specific tag
+        /// </summary>
+        /// <param name="tag"></param>
+        /// <returns></returns>
+        Task EvictByTag(string tag);
+    }
+
     /// <inheritdoc cref="IOutputCacheService" />
     [PrivateApi("Don't show in the documentation, as everything should use the Interface")]
     public class OutputCacheService : ServiceBase, IOutputCacheService