Added unit test to ensure default header contains User-Agent

BasicUnitTest/RestCallServiceTest.cs

+using System.Net.Http;
 using FitConnect.Services;
+using FluentAssertions;
 using Microsoft.Extensions.Logging;
 using NUnit.Framework;
 
 namespace BasicUnitTest;
 
 internal class DummyRestService : RestCallService {
-    public DummyRestService(string baseUrl) : base(baseUrl, null) {
+    public DummyRestService() : base("https://www.google.com", null) {
     }
+
+    public HttpClient GetClient() => CreateClient();
 }
 
 public class RestCallServiceTest {
-    
-    
     [Test]
     public void RestCallShouldContainVersionHeader() {
-        var restCallService = new DummyRestService("");
-          
+        var restCallService = new DummyRestService();
+        var client = restCallService.GetClient();
+        client.DefaultRequestHeaders.Contains("User-Agent").Should().BeTrue();
+        client.DefaultRequestHeaders.GetValues("User-Agent").Should()
+            .ContainMatch("FITConnectDotNetSDK*");
     }
-
 }

FitConnect/Services/RestCallService.cs

@@ -31,6 +31,7 @@ internal class RestCallService : IRestCallService {
         };
         var client = new HttpClient(clientHandler);
         client.DefaultRequestHeaders.Add("Accept", "application/json");
+        client.DefaultRequestHeaders.Add("User-Agent", GetVersionHeader());
         if (AccessToken != null)
             client.DefaultRequestHeaders.Add("Authorization", $"Bearer {AccessToken}");
         return client;
@@ -54,11 +55,15 @@ internal class RestCallService : IRestCallService {
             accept);
     }
 
+    private static string? _versionHeader;
+
     internal static string GetVersionHeader() {
+        if (_versionHeader != null) return _versionHeader;
         var version = ProjectSpecification.PackageVersion;
         var commit = ProjectSpecification.CommitId;
         var osVersion = Environment.OSVersion.Platform.ToString() + Environment.OSVersion.Version;
-        return $"FITConnectDotNetSDK/{version} (commit:{commit}; os:{osVersion})";
+        _versionHeader = $"FITConnectDotNetSDK/{version} (commit:{commit}; os:{osVersion})";
+        return _versionHeader;
     }
 
     protected async Task<string> RestCallForString(Uri requestUri, HttpMethod method,
@@ -83,7 +88,8 @@ internal class RestCallService : IRestCallService {
             _logger?.LogTrace("Body: {Body}", body);
         }
 
-        request.Headers.Add("User-Agent", GetVersionHeader());
+#warning moved to CreateClient
+        // request.Headers.Add("User-Agent", GetVersionHeader());
 
         var response = await client.SendAsync(request);