added memory cache for items count

Signed-off-by: David Hernando <[email protected]>

Docs/Demos/NCTLWebExplorer/Services/MysqlEventStore.cs

@@ -487,7 +487,7 @@ private async Task<int> GetItemsCount(MySqlConnection connection, string entity)
             {
                 AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(15)
             };
-            _memoryCache.Set(entity, countItems, cacheEntryOptions);
+            _memoryCache.Set(entity + "Count", countItems, cacheEntryOptions);
 
             return countItems;
         }