Add support for filter_properties in Database query api query params

Src/Notion.Client/Api/Databases/DatabasesClient.cs

@@ -1,4 +1,6 @@
-using System.Threading;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
 using System.Threading.Tasks;
 using static Notion.Client.ApiEndpoints;
 
@@ -23,8 +25,17 @@ public async Task<PaginatedList<Page>> QueryAsync(
             DatabasesQueryParameters databasesQueryParameters, CancellationToken cancellationToken = default)
         {
             var body = (IDatabaseQueryBodyParameters)databasesQueryParameters;
+            var queryParameters = (IDatabaseQueryQueryParameters)databasesQueryParameters;
 
-            return await _client.PostAsync<PaginatedList<Page>>(DatabasesApiUrls.Query(databaseId), body, cancellationToken: cancellationToken);
+            var queryParams = queryParameters.FilterProperties?
+                .Select(x => new KeyValuePair<string, string>("filter_properties", x));
+
+            return await _client.PostAsync<PaginatedList<Page>>(
+                DatabasesApiUrls.Query(databaseId),
+                body,
+                queryParams,
+                cancellationToken: cancellationToken
+            );
         }
 
         public async Task<Database> CreateAsync(DatabasesCreateParameters databasesCreateParameters, CancellationToken cancellationToken = default)

Src/Notion.Client/Api/Databases/RequestParams/DatabasesQueryParameters.cs

@@ -2,7 +2,7 @@
 
 namespace Notion.Client
 {
-    public class DatabasesQueryParameters : IDatabaseQueryBodyParameters
+    public class DatabasesQueryParameters : IDatabaseQueryBodyParameters, IDatabaseQueryQueryParameters
     {
         public Filter Filter { get; set; }
 
@@ -11,5 +11,7 @@ public class DatabasesQueryParameters : IDatabaseQueryBodyParameters
         public string StartCursor { get; set; }
 
         public int? PageSize { get; set; }
+
+        public List<string> FilterProperties { get; set; }
     }
 }

Src/Notion.Client/Api/Databases/RequestParams/IDatabaseQueryQueryParameters.cs

@@ -0,0 +1,11 @@
+using System.Collections.Generic;
+using Newtonsoft.Json;
+
+namespace Notion.Client
+{
+    public interface IDatabaseQueryQueryParameters
+    {
+        [JsonProperty("filter_properties")]
+        List<string> FilterProperties { get; set; }
+    }
+}

Src/Notion.Client/RestClient/IRestClient.cs

@@ -17,7 +17,7 @@ Task<T> GetAsync<T>(
         Task<T> PostAsync<T>(
             string uri,
             object body,
-            IDictionary<string, string> queryParams = null,
+            IEnumerable<KeyValuePair<string, string>> queryParams = null,
             IDictionary<string, string> headers = null,
             JsonSerializerSettings serializerSettings = null,
             CancellationToken cancellationToken = default);

Src/Notion.Client/RestClient/RestClient.cs

@@ -45,7 +45,7 @@ public async Task<T> GetAsync<T>(
         public async Task<T> PostAsync<T>(
             string uri,
             object body,
-            IDictionary<string, string> queryParams = null,
+            IEnumerable<KeyValuePair<string, string>> queryParams = null,
             IDictionary<string, string> headers = null,
             JsonSerializerSettings serializerSettings = null,
             CancellationToken cancellationToken = default)
@@ -125,7 +125,7 @@ private static async Task<Exception> BuildException(HttpResponseMessage response
         private async Task<HttpResponseMessage> SendAsync(
             string requestUri,
             HttpMethod httpMethod,
-            IDictionary<string, string> queryParams = null,
+            IEnumerable<KeyValuePair<string, string>> queryParams = null,
             IDictionary<string, string> headers = null,
             Action<HttpRequestMessage> attachContent = null,
             CancellationToken cancellationToken = default)
@@ -176,7 +176,7 @@ private void EnsureHttpClient()
             _httpClient.BaseAddress = new Uri(_options.BaseUrl);
         }
 
-        private static string AddQueryString(string uri, IDictionary<string, string> queryParams)
+        private static string AddQueryString(string uri, IEnumerable<KeyValuePair<string, string>> queryParams)
         {
             return queryParams == null ? uri : QueryHelpers.AddQueryString(uri, queryParams);
         }

Src/Notion.Client/http/QueryHelpers.cs

@@ -45,7 +45,7 @@ public static string AddQueryString(string uri, IDictionary<string, string> quer
             return AddQueryString(uri, (IEnumerable<KeyValuePair<string, string>>)queryParams);
         }
 
-        private static string AddQueryString(
+        public static string AddQueryString(
             string uri,
             IEnumerable<KeyValuePair<string, string>> queryParams)
         {