fix: loading of header reference description

Signed-off-by: Vincent Biret <vibiret@microsoft.com>

Author: baywet

src/Microsoft.OpenApi/Reader/V31/OpenApiHeaderDeserializer.cs

@@ -114,7 +114,9 @@ public static IOpenApiHeader LoadHeader(ParseNode node, OpenApiDocument hostDocu
             if (pointer != null)
             {
                 var reference = GetReferenceIdAndExternalResource(pointer);
-                return new OpenApiHeaderReference(reference.Item1, hostDocument, reference.Item2);
+                var headerReference = new OpenApiHeaderReference(reference.Item1, hostDocument, reference.Item2);
+                headerReference.Reference.SetMetadataFromMapNode(mapNode);
+                return headerReference;
             }
 
             var header = new OpenApiHeader();

test/Microsoft.OpenApi.Readers.Tests/V31Tests/OpenApiHeaderReferenceDeserializerTests.cs

@@ -0,0 +1,39 @@
+
+using System.Text.Json.Nodes;
+using Microsoft.OpenApi.Reader;
+using Microsoft.OpenApi.Reader.V31;
+using Xunit;
+
+namespace Microsoft.OpenApi.Readers.Tests.V31Tests;
+
+public class OpenApiHeaderReferenceDeserializerTests
+{
+    [Fact]
+    public void ShouldDeserializeReferenceAnnotations()
+    {
+        var json =
+        """
+        {
+            "$ref": "#/components/headers/MyHeader",
+            "description": "This is a header reference"
+        }
+        """;
+
+        var hostDocument = new OpenApiDocument();
+        hostDocument.AddComponent("MyHeader", new OpenApiHeader
+        {
+            Description = "This is a header"
+        });
+        var jsonNode = JsonNode.Parse(json);
+        var parseNode = ParseNode.Create(new ParsingContext(new()), jsonNode);
+
+        var result = OpenApiV31Deserializer.LoadHeader(parseNode, hostDocument);
+
+        Assert.NotNull(result);
+        var resultReference = Assert.IsType<OpenApiHeaderReference>(result);
+
+        Assert.Equal("MyHeader", resultReference.Reference.Id);
+        Assert.Equal("This is a header reference", resultReference.Description);
+        Assert.NotNull(resultReference.Target);
+    }
+}