Fix nginx.conf for reverse-proxy with HTTPS

[hwiorn]

Related #77, #264.

This PR changes the nginx.conf of wallabag-docker to enable fastcgi HTTPS especially in case of reverse-proxy settings.

The idea is came from @blopware 's workaround and https://serverfault.com/a/527809.

[ngosang]

@Kdecherf @j0k3r I tested this PR and I confirm it fixes #77
Tested several scenarios:

• Direct connection to Wallabag Docker (HTTP) => OK
• Traefik (HTTPS reverse proxy) => Wallabag Docker (HTTP) => OK

There are several issues in wallabag android app caused by #77 that will be fixed too.

[Hodapp87]

This fixed some of my issues when putting this Docker container behind a reverse proxy, but Wallabag is still mangling URLs (e.g. dropping port number for no reason)

[LeonardoMantovani]

I tested those changes in my setup where I run Wallabag+MariaDB behind Traefik v2 and they solved the problem I had (https://mywallabag.com redirecting to http://mywallabag.com/login instead of the https one).
I didn't experienced any issue with those changes.
I think the PR should be merged.

[ngosang]

@j0k3r could you include this in the next release?

[LeonardoMantovani]

I don't know how GitHub PR automation works but it seems they need 1 more approved review to proceed with merging. I already did it, maybe someone else could try to do it too?

[Cycatz]

I got HTTP redirection loop like this
https://mydomain/ -> http://mydomain/login -> https://mydomain/
This caused the Unknown error: Too many follow-up requests: 21 error on Android app upon login
This fixed the redirect issue with nginx->podman container setup and I hope this to be merged

[GeorgFoc]

I can confirm, this fix worked. Pls bring this PR into main

[ngosang]

@Kdecherf could you merge?

[ngosang]

@wallabag/core could you merge? This PR is really important to make Reverse Proxies to work. It's tested by me.