Add varchar(max) support in DTO attributes

[SpecialDbType(SpecialDbTypes.NVARCHARMAX)]

src/Umbraco.Core/Persistence/SqlSyntax/SqlSyntaxProviderBase.cs

@@ -196,7 +196,13 @@ namespace Umbraco.Core.Persistence.SqlSyntax
                 return "NCHAR";
             }
             else if (dbTypes == SpecialDbTypes.NTEXT)
+            {
                 return "NTEXT";
+            }
+            else if (dbTypes == SpecialDbTypes.NVARCHARMAX)
+            {
+                return "NVARCHAR(MAX)";
+            }
 
             return "NVARCHAR";
         }