Add BuildQueryFromObject<T> method for query strings

Enhanced ReCClientHelpers.cs with a new utility method:
- Added `BuildQueryFromObject<T>` to serialize objects into query strings.
- Skips `null` properties and escapes names/values for safety.
- Added `System.Collections` and `System.Reflection` namespaces to support reflection and collection operations.

This improves HTTP request handling by enabling dynamic query string generation from object payloads.

src/ReC.Client/ReCClientHelpers.cs

@@ -1,8 +1,10 @@
 using System;
+using System.Collections;
 using System.Globalization;
 using System.Linq;
 using System.Net.Http;
 using System.Net.Http.Json;
+using System.Reflection;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
@@ -46,6 +48,30 @@ namespace ReC.Client
         /// <returns>A <see cref="JsonContent"/> instance ready for HTTP requests.</returns>
         public static JsonContent ToJsonContent<T>(T payload) => JsonContent.Create(payload);
 
+        /// <summary>
+        /// Builds a query string from the public readable properties of <paramref name="payload"/>,
+        /// skipping properties whose values are <see langword="null"/>.
+        /// </summary>
+        /// <typeparam name="T">The payload type.</typeparam>
+        /// <param name="payload">The payload to serialize into a query string.</param>
+        /// <returns>A query string beginning with '?', or an empty string if no values are provided.</returns>
+        public static string BuildQueryFromObject<T>(T payload)
+        {
+            if (payload == null)
+                return string.Empty;
+
+            var props = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance)
+                .Where(p => p.CanRead && p.GetIndexParameters().Length == 0);
+
+            var parts = props
+                .Select(p => new { p.Name, Value = p.GetValue(payload) })
+                .Where(p => p.Value != null)
+                .Select(p => $"{Uri.EscapeDataString(p.Name)}={Uri.EscapeDataString(Convert.ToString(p.Value, CultureInfo.InvariantCulture) ?? string.Empty)}");
+
+            var query = string.Join("&", parts);
+            return string.IsNullOrWhiteSpace(query) ? string.Empty : $"?{query}";
+        }
+
         /// <summary>
         /// Logs the outcome of an HTTP response. Throws a <see cref="ReCApiException"/> when the
         /// response indicates a non-success status code; otherwise (optionally) writes an informational