feat: Add support for HTTP response trailers

src/RestSharp/Response/RestResponse.cs

@@ -73,6 +73,9 @@ async Task<RestResponse> GetDefaultResponse() {
                 Server              = httpResponse.Headers.Server.ToString(),
                 StatusCode          = httpResponse.StatusCode,
                 StatusDescription   = httpResponse.ReasonPhrase,
+#if NET
+                TrailingHeaders     = httpResponse.TrailingHeaders.GetHeaderParameters(),
+#endif
                 Version             = httpResponse.RequestMessage?.Version
             };
         }

src/RestSharp/Response/RestResponseBase.cs

@@ -111,6 +111,11 @@ protected RestResponseBase(RestRequest request) {
     /// </summary>
     public IReadOnlyCollection<HeaderParameter>? ContentHeaders { get; set; }
 
+    /// <summary>
+    /// Trailer headers returned by server with the response
+    /// </summary>
+    public IReadOnlyCollection<HeaderParameter>? TrailingHeaders { get; set; }
+
     /// <summary>
     /// Status of the request. Will return Error for transport errors.
     /// HTTP errors will still return ResponseStatus.Completed, check StatusCode instead

test/RestSharp.Tests.Integrated/ResponseTrailerTests.cs

@@ -0,0 +1,29 @@
+#if NET8_0_OR_GREATER
+using System.Net;
+using System.Net.Http;
+
+namespace RestSharp.Tests.Integrated;
+
+public class ResponseTrailerTests {
+    [Fact]
+    public async Task Response_trailers_are_preserved_separately_from_headers() {
+        using var client = new RestClient(new TrailerResponseHandler());
+
+        var response = await client.ExecuteAsync(new RestRequest("https://example.test/"));
+
+        response.TrailingHeaders.Should().ContainSingle(header => header.Name == "Checksum" && header.Value == "abc123");
+        response.Headers.Should().NotContain(header => header.Name == "Checksum");
+        response.ContentHeaders.Should().NotContain(header => header.Name == "Checksum");
+    }
+
+    sealed class TrailerResponseHandler : HttpMessageHandler {
+        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) {
+            var response = new HttpResponseMessage(HttpStatusCode.OK) {
+                Content = new StringContent("body")
+            };
+            response.TrailingHeaders.TryAddWithoutValidation("Checksum", "abc123");
+            return Task.FromResult(response);
+        }
+    }
+}
+#endif