resolves #4899: output cache for sitemap

Oqtane.Client/Services/Interfaces/ICacheService.cs

@@ -0,0 +1,18 @@
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Oqtane.Services
+{
+    /// <summary>
+    /// Service to manage cache
+    /// </summary>
+    public interface ICacheService
+    {
+        /// <summary>
+        /// Evicts the output cache for a specific tag
+        /// </summary>
+        /// <param name="tag"></param>
+        /// <returns></returns>
+        Task EvictOutputCacheByTag(string tag, CancellationToken cancellationToken = default);
+    }
+}