Authentication redirects to localhost:3000 instead of real site

For the deployment at o3web.test.fedcloud.eu, an attempt to login via EGI Check-In, redirects to "localhost:3000" instead of the running at o3web.test.fedcloud.eu instance. It could also be useful to use another than port 3000, because docker-compose sets port match "80" on the host to "3000" in the container.