Expose HTTP response trailing headers

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
             };
         }
@@ -94,4 +97,4 @@ public RestResponse() : this(new()) { }
     }
 }
 
-public delegate ResponseStatus CalculateResponseStatus(HttpResponseMessage httpResponse);
+public delegate ResponseStatus CalculateResponseStatus(HttpResponseMessage httpResponse);

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 after the response content
+    /// </summary>
+    public IReadOnlyCollection<HeaderParameter> TrailingHeaders { get; set; } = Array.Empty<HeaderParameter>();
+
     /// <summary>
     /// Status of the request. Will return Error for transport errors.
     /// HTTP errors will still return ResponseStatus.Completed, check StatusCode instead

test/RestSharp.Tests/ResponseTrailerTests.cs

@@ -0,0 +1,37 @@
+using System.Net;
+
+namespace RestSharp.Tests;
+
+public class ResponseTrailerTests {
+#if NET
+    [Fact]
+    public async Task Should_map_trailing_headers_separately_from_regular_headers() {
+        using var client = new RestClient(
+            new RestClientOptions("https://dummy.org") { ConfigureMessageHandler = _ => new TrailerResponseHandler() }
+        );
+
+        var response = await client.ExecuteAsync(new RestRequest());
+
+        response.TrailingHeaders.Should().BeEquivalentTo(
+            new[] {
+                new HeaderParameter("Digest", "sha-256=abc"),
+                new HeaderParameter("Digest", "sha-256=def"),
+                new HeaderParameter("X-Processing-Status", "complete")
+            }
+        );
+        response.Headers.Should().ContainSingle(x => x.Name == "X-Regular-Header" && x.Value == "regular");
+        response.Headers.Should().NotContain(x => x.Name == "Digest" || x.Name == "X-Processing-Status");
+        response.ContentHeaders.Should().NotContain(x => x.Name == "Digest" || x.Name == "X-Processing-Status");
+    }
+
+    class TrailerResponseHandler : HttpMessageHandler {
+        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) {
+            var response = new HttpResponseMessage(HttpStatusCode.OK) { Content = new StringContent("{}") };
+            response.Headers.TryAddWithoutValidation("X-Regular-Header", "regular");
+            response.TrailingHeaders.TryAddWithoutValidation("Digest", ["sha-256=abc", "sha-256=def"]);
+            response.TrailingHeaders.TryAddWithoutValidation("X-Processing-Status", "complete");
+            return Task.FromResult(response);
+        }
+    }
+#endif
+}