[server-ce] nginx: make keepalive_timeout configurable GitOrigin-RevId: 3a0bb049b57f0a4ee065c86463fd6300d97934c7
* Add envsubst binary to image * Generate nginx.conf from template, with env-vars * Remove nginx.conf, now generated from template * Reload nginx config after writing file Co-authored-by: Shane Kilkelly <shane.kilkelly@overleaf.com>