Add support for HTTP(S) proxies

[cthu1hoo]

Requirements

• Is this a feature request? For questions or discussions use https://lemmy.ml/c/lemmy_support
• Did you check to see if this issue already exists?
• Is this only a feature request? Do not put multiple feature requests in one issue.
• Is this a backend issue? Use the lemmy-ui repo for UI / frontend issues.

Is your proposal related to a problem?

Outbound HTTP requests backend makes would fail if Lemmy instance has no direct outbound internet connection.

Describe the solution you'd like.

Please consider adding HTTP(S) proxy support for outgoing requests, HTTP_PROXY environment variable is an industry standard, of sorts. Config option would also work, of course.

Thanks in advance.

Describe alternatives you've considered.

I've thought about things like routing Lemmy backend container traffic via wireguard client container but I'd rather not. :)

Additional context

No response

[dhawos]

I think this is actually already supported from what I can read in the documentation from the library that is used to make those request : https://docs.rs/reqwest/latest/reqwest/index.html#proxies

I've tried to set the variables locally to an invalid address and the requests failed, when they succeeded if I did not set these variables

[cthu1hoo]

I've tried setting HTTP_PROXY for the lemmy (backend) container and it broke the whole thing for me, i.e. white page with "Server error" and that's it.

Proxy logs show that inter-container traffic within lemmy compose setup also goes through the proxy, which obviously is not aware of http://pictrs/... and any other non-fqdn names which only resolve inside the container. So those need to be excluded somehow.