fixup! fix(transport): header override, gzip pool, body-read error, and body-close correctness (opensearch-project#859)

Signed-off-by: Sean Chittenden <sean.chittenden@crowdstrike.com>

Author: sean-

response_test.go

@@ -23,6 +23,7 @@ package opensearch_test
 
 import (
 	"errors"
+	"fmt"
 	"io"
 	"net/http"
 	"strings"
@@ -34,6 +35,20 @@ import (
 	"github.com/opensearch-project/opensearch-go/v5"
 )
 
+// String uses a pointer receiver because it is non-consuming: it restores Body
+// after rendering, which mutates the receiver. Consequently only *Response
+// satisfies fmt.Stringer; a Response value deliberately does not, so passing a
+// value to fmt.Print*/Sprintf("%s", ...) is a mistake the compiler cannot catch.
+// This guard pins the pointer contract; TestResponseValueNotStringer pins the
+// value gap so a revert to a value receiver fails the build.
+var _ fmt.Stringer = (*opensearch.Response)(nil)
+
+func TestResponseValueNotStringer(t *testing.T) {
+	var v any = opensearch.Response{}
+	_, ok := v.(fmt.Stringer)
+	require.False(t, ok, "Response value must not satisfy fmt.Stringer; String() is pointer-receiver on v5")
+}
+
 func TestResponse(t *testing.T) {
 	t.Run("empty response", func(t *testing.T) {
 		resp := opensearch.NewResponse(0, nil, nil)