added cache pipelines

NzbDrone.Api/Extensions/Pipelines/CacheHeaderPipeline.cs

@@ -0,0 +1,34 @@
+using System;
+using Nancy;
+using Nancy.Bootstrapper;
+using NzbDrone.Api.Frontend;
+
+namespace NzbDrone.Api.Extensions.Pipelines
+{
+    public class CacheHeaderPipeline : IRegisterNancyPipeline
+    {
+        private readonly ICacheableSpecification _cacheableSpecification;
+
+        public CacheHeaderPipeline(ICacheableSpecification cacheableSpecification)
+        {
+            _cacheableSpecification = cacheableSpecification;
+        }
+
+        public void Register(IPipelines pipelines)
+        {
+            pipelines.AfterRequest.AddItemToStartOfPipeline(Handle);
+        }
+
+        private void Handle(NancyContext context)
+        {
+            if (_cacheableSpecification.IsCacheable(context))
+            {
+                context.Response.Headers.EnableCache();
+            }
+            else
+            {
+                context.Response.Headers.DisableCache();
+            }
+        }
+    }
+}