Wildcard router doesn't correctly pass headers with underscore in name

When 3scale amp is configured with wildcard router, the headers, which name contains underscore, are passed neither to production nor to staging apicasts.

Any request to service with header where is underscore fails with 403 status code and Authentication parameters missing. message.

This issue affects services with AppId AppKey authentication, where header names for app_id and app_key contains underscores by default.