Add project files

StalwartSDK/StalwartClientFactory.cs

@@ -0,0 +1,23 @@
+using System.Net.Http.Headers;
+
+namespace AdOrbitSDK;
+
+public partial class Client
+{
+    private readonly string _apiKey;
+
+    public Client(HttpClient httpClient, string apiKey)
+        : this(httpClient)
+    {
+        _apiKey = apiKey;
+    }
+
+    partial void PrepareRequest(HttpClient client, HttpRequestMessage request, string url)
+    {
+        if (client.BaseAddress == null) throw new NullReferenceException("Base address cannot be null");
+
+        var authHeader = new AuthenticationHeaderValue("Bearer", _apiKey);
+
+        request.Headers.Authorization = authHeader;
+    }
+}