fix: Unique Id property parsing

Author: RandomUser14

Src/Notion.Client/Models/PropertyValue/PropertyValue.cs

@@ -29,6 +29,7 @@ namespace Notion.Client
     [JsonSubtypes.KnownSubTypeAttribute(typeof(StatusPropertyValue), PropertyValueType.Status)]
     [JsonSubtypes.KnownSubTypeAttribute(typeof(TitlePropertyValue), PropertyValueType.Title)]
     [JsonSubtypes.KnownSubTypeAttribute(typeof(UrlPropertyValue), PropertyValueType.Url)]
+    [JsonSubtypes.KnownSubTypeAttribute(typeof(UniqueIdPropertyValue), PropertyValueType.UniqueId)]
     [SuppressMessage("ReSharper", "UnusedMember.Global")]
     [SuppressMessage("ReSharper", "UnassignedGetOnlyAutoProperty")]
     public class PropertyValue

Src/Notion.Client/Models/PropertyValue/PropertyValueType.cs

@@ -70,6 +70,9 @@ public enum PropertyValueType
         LastEditedBy,
 
         [EnumMember(Value = "status")]
-        Status
+        Status,
+
+        [EnumMember(Value = "unique_id")]
+        UniqueId,
     }
 }

Src/Notion.Client/Models/PropertyValue/UniqueIdPropertyValue.cs

@@ -0,0 +1,29 @@
+using System;
+using Newtonsoft.Json;
+
+namespace Notion.Client
+{
+    /// <summary>
+    ///     Unique Id property value object.
+    /// </summary>
+    public class UniqueIdPropertyValue : PropertyValue
+    {
+        public override PropertyValueType Type => PropertyValueType.UniqueId;
+
+        /// <summary>
+        ///     Unique Id property of database item
+        /// </summary>
+        [JsonProperty("unique_id")]
+        public UniqueIdValue UniqueId { get; set; }
+    }
+
+    public class UniqueIdValue
+    {
+        [JsonProperty("prefix")]
+        public string Prefix { get; set; }
+
+        [JsonProperty("number")]
+        public double? Number { get; set; }
+    }
+}
+