Adding str length annotation to model

--HG--
branch : dev

src/Orchard.Web/Modules/Orchard.Media/Models/MediaSettingsPartRecord.cs

@@ -7,6 +7,7 @@ namespace Orchard.Media.Models {
         internal const string DefaultWhitelist = "jpg jpeg gif png txt doc docx xls xlsx pdf ppt pptx pps ppsx odt ods odp";
         private string _whitelist = DefaultWhitelist;
 
+        [StringLength(255)]
         public virtual string UploadAllowedFileTypeWhitelist {
             get { return _whitelist; }
             set { _whitelist = value; }