fix birthday nullable

Src/Dlhis.Basic/Organization/Response/GainfoCurrentResponse.cs

@@ -45,8 +45,13 @@ public class GainfoCurrentResponse
     /// <summary>
     /// 出生日期/生日
     /// </summary>
-    [JsonConverter(typeof(ToDateJsonConverter))]
-    public DateTime Birthday { get; set; }
+    public string Birthday
+    {
+        get { return OriginalBirthday.HasValue ? OriginalBirthday.Value.ToString("yyyy-MM-dd") : "0000-00-00"; }
+    }
+
+
+    public DateTime? OriginalBirthday { get; set; }
 
     /// <summary>
     /// 厂区编码