attachment apis and azure storage service

src/Core/Services/IAttachmentStorageService.cs

@@ -0,0 +1,11 @@
+using System.IO;
+using System.Threading.Tasks;
+
+namespace Bit.Core.Services
+{
+    public interface IAttachmentStorageService
+    {
+        Task UploadAttachmentAsync(Stream stream, string name);
+        Task DeleteAttachmentAsync(string name);
+    }
+}