identity: use Quartz.NET for token cleanup

Streetwriters.Identity/Jobs/TokenCleanupJob.cs

@@ -0,0 +1,20 @@
+using System.Threading.Tasks;
+using Quartz;
+using Streetwriters.Identity.Services;
+
+namespace Streetwriters.Identity.Jobs
+{
+    public class TokenCleanupJob : IJob
+    {
+        private TokenCleanup TokenCleanup { get; set; }
+        public TokenCleanupJob(TokenCleanup tokenCleanup)
+        {
+            TokenCleanup = tokenCleanup;
+        }
+
+        public Task Execute(IJobExecutionContext context)
+        {
+            return TokenCleanup.RemoveExpiredGrantsAsync();
+        }
+    }
+}