Node.js Http2ServerResponse.getHeaderNames() Method

Node.js has introduced the `Http2ServerResponse.getHeaderNames()` method, which returns an array of all HTTP response header names that have been set on an HTTP/2 server response. This allows developers to inspect which headers are queued for transmission before the response is sent to the client. The method is called directly on an `Http2ServerResponse` object and returns unique header names as an array. It works with headers set via `setHeader()`, including multi-value headers like `Set-Cookie`. Examples demonstrate its use in server handlers to log or verify header configuration, with outputs showing arrays of header names such as `content-type` or `foo` and `set-cookie`. This method is primarily useful for debugging and validating response header setup during development. It helps developers confirm that expected headers are present, identify missing or incorrectly configured headers, and inspect header information before modifying or removing them. It is part of Node.js's HTTP/2 module, which requires TLS certificates for server setup.