add VerificationProperty

Author: kosaku-hayashi

Src/Notion.Client/Models/Database/Properties/Property.cs

@@ -27,6 +27,7 @@ namespace Notion.Client
     [JsonSubtypes.KnownSubTypeAttribute(typeof(UrlProperty), PropertyType.Url)]
     [JsonSubtypes.KnownSubTypeAttribute(typeof(UniqueIdProperty), PropertyType.UniqueId)]
     [JsonSubtypes.KnownSubTypeAttribute(typeof(ButtonProperty), PropertyType.Button)]
+    [JsonSubtypes.KnownSubTypeAttribute(typeof(VerificationProperty), PropertyType.Verification)]
     public class Property
     {
         [JsonProperty("id")]

Src/Notion.Client/Models/Database/Properties/PropertyType.cs

@@ -74,5 +74,8 @@ public enum PropertyType
 
         [EnumMember(Value = "button")]
         Button,
+
+        [EnumMember(Value = "verification")]
+        Verification
     }
 }

Src/Notion.Client/Models/Database/Properties/VerificationProperty.cs

@@ -0,0 +1,13 @@
+using System.Collections.Generic;
+using Newtonsoft.Json;
+
+namespace Notion.Client
+{
+    public class VerificationProperty : Property
+    {
+        public override PropertyType Type => PropertyType.Verification;
+
+        [JsonProperty("verification")]
+        public Dictionary<string, object> Verification { get; set; }
+    }
+}