Headless Configuration Issue behind a proxy solved

When Headless-Server is running behind a reverse proxy, it is necessary to set a Spring configuration property to make Swagger work correctly. The configuration property `server.forward-headers-strategy`should be set to the value `framework`. This can be done either by application properties or preferably by environment variable, like `SERVER_FORWARD_HEADERS_STRATEGY: "framework"`.

(CMS-24719)