feat: support external proxies

[teidesu]

added support for API_EXTERNAL_PROXY env variable that sets up a global undici dispatcher

definitely not the best way to do this (i really dislike relying on globals), but did it like this anyway because:

• there isn't a single common wrapper over fetch() where i could provide a dispatcher
• passing it manually everywhere is very tedious and error-prone (especially considering there aren't any types)
• since api is supposed to run in a separate isolated process it probably won't affect what it isn't supposed to

one thing i worry about is the youtube handler which mentions reading dispatcher from streamInfo, but i couldn't find a place where it is being passed there 🧐

[dumbmoron]

one thing i worry about is the youtube handler which mentions reading dispatcher from streamInfo, but i couldn't find a place where it is being passed there 🧐

it's passed in from match.js if freebind is enabled (FREEBIND_CIDR has a value and syscall-napi compiled successfully).

it's only passed to some services that need it (youtube, twitter and instagram), because, as you mentioned, passing it manually everywhere is very tedious

[dumbmoron]

also it would be worth to mention that ProxyAgent only supports http(s)? proxies, so to fully support everything including using a socks proxy you would need to use something like fetch-socks

[teidesu]

only supports http(s)? proxies

yeah, and i mentioned it in the docs too. i personally don't think supporting socks is really worth it:

• most of the (paid) proxy services provide both http and socks endpoints
• most of the local software (e.g. xray-core and sing-box) have a "mixed" inbound that accepts both http and socks
• if someone still wants to use socks proxy – they can use privoxy or whatever to convert it to http proxy

if one day undici ends up supporting socks (nodejs/undici#2224) we would get socks support for free :D

regarding the freebind dispatcher - i suppose we should error if freebind is enabled and proxy is passed, because there really isn't much point in using both of them at the same time

[dumbmoron]

@teidesu

i suppose we should error if freebind is enabled and proxy is passed, because there really isn't much point in using both of them at the same time

could you add that? otherwise lgtm