Add federation tracing extension method

src/Transports.AspNetCore/Extensions/GraphQLHttpRequestExtensions.cs

@@ -0,0 +1,25 @@
+namespace GraphQL.Utilities.Federation;
+
+/// <summary>
+/// <see cref="HttpRequest" /> extension methods for checking headers.
+/// </summary>
+public static class GraphQLHttpRequestExtensions
+{
+    private const string HEADER_NAME = "apollo-federation-include-trace";
+    private const string HEADER_VALUE = "ftv1";
+
+    /// <summary>
+    /// Determines if federated tracing is enabled through HTTP headers.
+    /// </summary>
+    /// <returns><see langword="true"/> if the 'apollo-federation-include-trace' HTTP header has a value of 'ftv1'</returns>
+    public static bool IsApolloFederatedTracingEnabled(this HttpRequest request)
+    {
+        var headers = request?.Headers;
+        if (headers != null && headers.TryGetValue(HEADER_NAME, out var values))
+        {
+            var value = values.FirstOrDefault();
+            return HEADER_VALUE.Equals(value, StringComparison.OrdinalIgnoreCase);
+        }
+        return false;
+    }
+}

tests/ApiApprovalTests/net5+netcoreapp31/GraphQL.Server.Transports.AspNetCore.approved.txt

@@ -377,6 +377,13 @@ namespace GraphQL
             where TWebSocketAuthenticationService :  class, GraphQL.Server.Transports.AspNetCore.WebSockets.IWebSocketAuthenticationService { }
     }
 }
+namespace GraphQL.Utilities.Federation
+{
+    public static class GraphQLHttpRequestExtensions
+    {
+        public static bool IsApolloFederatedTracingEnabled(this Microsoft.AspNetCore.Http.HttpRequest request) { }
+    }
+}
 namespace Microsoft.AspNetCore.Builder
 {
     public class GraphQLEndpointConventionBuilder : Microsoft.AspNetCore.Builder.IEndpointConventionBuilder

tests/ApiApprovalTests/netcoreapp21+netstandard20/GraphQL.Server.Transports.AspNetCore.approved.txt

@@ -395,6 +395,13 @@ namespace GraphQL
             where TWebSocketAuthenticationService :  class, GraphQL.Server.Transports.AspNetCore.WebSockets.IWebSocketAuthenticationService { }
     }
 }
+namespace GraphQL.Utilities.Federation
+{
+    public static class GraphQLHttpRequestExtensions
+    {
+        public static bool IsApolloFederatedTracingEnabled(this Microsoft.AspNetCore.Http.HttpRequest request) { }
+    }
+}
 namespace Microsoft.AspNetCore.Builder
 {
     public static class GraphQLHttpApplicationBuilderExtensions