Proxy request method, headers and body with sendProxy()

[P4sca1]

I would expect sendProxy to copy method, headers and body from the original request.

// Copy request method
const method = event.req.method

// Copy request headers
const ignoredHeaders = [
	// https://github.com/nodejs/undici/blob/cd78eb57203ce85a26312290c1bef4017e30cf74/lib/core/request.js#L196-L220
	'transfer-encoding',
	'connection',
	'keep-alive',
	'upgrade',
	'expect',
]
const headers: HeadersInit = {}
for (const [header, value] of Object.entries(getRequestHeaders(event))) {
	if (value === undefined || ignoredHeaders.includes(header)) continue
	headers[header] = value
}
// TODO: Set x-forwarder-* headers?

// Copy request body
const payloadMethods = ['PATCH', 'POST', 'PUT', 'DELETE']
const body = payloadMethods.includes(method)
	? await (readRawBody(event, false) as unknown as Promise<Buffer>) // https://github.com/unjs/h3/issues/223
	: undefined

sendProxy(event, target.toString(), {
	fetchOptions: { method, headers, body },
})

[pi0]

Normally sendProxy is an explicit method to send response as proxy. We can create few options like passHeaders: true or proxyHeaders: true (same for body and method) to extend functionality.

[pi0]

Added a basic implementation in #226

Feel free to open a PR to improve options. I think both X-Forwarded-For support and making ignore configurable are good ideas!