chore(header): Add support for RFC 9512: application/yaml (#3851)

* fix(binding): support application/yaml

RFC 9512 defines application/yaml as the official YAML MIME type.
application/x-yaml is deprecated. In this commit, we ensure it is
recognized correctly in Content-Type.

* fix(render): use application/yaml when rendering YAML

As per RFC 9512, application/x-yaml is now deprecated and applications
should use application/yaml. This commit fix the Content-Type header
when rendering YAML.

binding/binding_nomsgpack.go

@@ -19,6 +19,7 @@ const (
 	MIMEMultipartPOSTForm = "multipart/form-data"
 	MIMEPROTOBUF          = "application/x-protobuf"
 	MIMEYAML              = "application/x-yaml"
+	MIMEYAML2             = "application/yaml"
 	MIMETOML              = "application/toml"
 )
 
@@ -96,7 +97,7 @@ func Default(method, contentType string) Binding {
 		return XML
 	case MIMEPROTOBUF:
 		return ProtoBuf
-	case MIMEYAML:
+	case MIMEYAML, MIMEYAML2:
 		return YAML
 	case MIMEMultipartPOSTForm:
 		return FormMultipart