Add behindProxy option to App.listen()

[dahlia]

Addresses #2660.

The behindProxy option lets Fresh respect X-Forwarded-Proto, X-Forwarded-Host, X-Forwarded-Port, and X-Forwarded-For headers (if any). This is useful when Fresh is behind a reverse proxy like nginx or Caddy.

[marvinhagemeister]

Thanks for making a PR. I feel like this is much better implemented as a middleware instead of a configuration option as it's not something everyone needs. With Fresh 2 the aim is to keep the config as minimal as possible.

[dahlia]

@marvinhagemeister Does Fresh's middleware support replacing request objects? At first glance, it doesn't seem to support that.

[marvinhagemeister]

Yes, to replace the Request object do this:

function proxyMiddleware(ctx) {
  const req =  new Request()
  
  // Replace current request
  ctx.req = req;
  ctx.url = new URL(req.url)
  
  return ctx.next()
}

[dahlia]

@marvinhagemeister Apparently FreshContext.req is readonly. Should I suppress the TypeScript error and set ctx.req by force?

[marvinhagemeister]

Let's remove the readonly in FreshContext.

[dahlia]

Let's remove the readonly in FreshContext.

@marvinhagemeister: Just opened a separate pull request.