Feature request: Provide an API to get file descriptor of the Socket connection

I have a specific use case. I’m using pekko server to handle REST APIs calls. I need to get the file descriptor associated with socket connection then pass it to some legacy C program.

I'd like to request an API to get the file descriptor associated with socket connection for GET/POST REST APIs calls.

No source file, test, or entry point is named. Start by locating the Pekko server request and socket-connection APIs, then determine how a file descriptor could be exposed for REST calls; done means a defined API and coverage for the requested GET/POST use case.

Written by the indexing model from the issue text.