HTTPS_PROXY / HTTP_PROXY?

Nobody has claimed this yet.

Hello

We are behind an outgoing proxy, and I suspect Mattermost not being able to connect to stuff

For example, docker logs mattermost :

```
{"timestamp":"2021-12-15 23:58:50.950 Z","level":"debug","msg":"ERROR: sending request - Post \"https://pdat.matterlytics.com/v1/batch\": context deadline exceeded (Client.Timeout exceeded while awaiting headers)","caller":"log/log.go:184","source":"rudder"}
```

I remember with a previous version of Mattermost (https://github.com/mattermost/mattermost-docker), I had to somehow configure outgoing http proxy. I precisely modified the Dockerfile to recompile it.

Please, what's the solution here?

Thanks!

Start by inspecting the repository's Dockerfile and configuration entry points for outgoing proxy settings, then compare them with the referenced mattermost-docker approach. Confirm the supported configuration path for HTTPS_PROXY and HTTP_PROXY and document or implement it so the reported outbound request can use the proxy.

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