chore: import upstream snapshot with attribution

pkg/http/transport/graphql_features.go

@@ -0,0 +1,52 @@
+package transport
+
+import (
+	"net/http"
+	"strings"
+
+	ghcontext "github.com/github/github-mcp-server/pkg/context"
+	"github.com/github/github-mcp-server/pkg/http/headers"
+)
+
+// GraphQLFeaturesTransport is an http.RoundTripper that adds GraphQL-Features
+// header to requests based on context values. This is required for using
+// non-GA GraphQL API features like the agent assignment API.
+//
+// This transport is used internally by the MCP server and is also exported
+// for library consumers who need to build their own HTTP clients with
+// GraphQL feature flag support.
+//
+// Usage:
+//
+//	import "github.com/github/github-mcp-server/pkg/http/transport"
+//
+//	httpClient := &http.Client{
+//	    Transport: &transport.GraphQLFeaturesTransport{
+//	        Transport: http.DefaultTransport,
+//	    },
+//	}
+//	gqlClient := githubv4.NewClient(httpClient)
+//
+// Then use ghcontext.WithGraphQLFeatures(ctx, "feature_name") when calling GraphQL operations.
+type GraphQLFeaturesTransport struct {
+	// Transport is the underlying HTTP transport. If nil, http.DefaultTransport is used.
+	Transport http.RoundTripper
+}
+
+// RoundTrip implements http.RoundTripper.
+func (t *GraphQLFeaturesTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	transport := t.Transport
+	if transport == nil {
+		transport = http.DefaultTransport
+	}
+
+	// Clone the request to avoid mutating the original
+	req = req.Clone(req.Context())
+
+	// Check for GraphQL-Features in context and add header if present
+	if features := ghcontext.GetGraphQLFeatures(req.Context()); len(features) > 0 {
+		req.Header.Set(headers.GraphQLFeaturesHeader, strings.Join(features, ", "))
+	}
+
+	return transport.RoundTrip(req)
+}