API V2 cache problem with custom configuration in nginx.conf.in

[submarcos]

API v2 responses doesn't take care about X-FORWARDED-PROTO value defined in nginx configuration.
This header is used by django to know if generated url (pictogram, attachment) is http or https.
In some cases, custom configuration in nginx.conf.in to work behind haproxy, API response does not match with headers.

For the moment, any change about it in nginx template should be followed by clearing api_v2 cache in admin panel