How to use environment variables to make a containerized Quarkus application more flexible

When you run a containerized application on a container orchestration platform like Kubernetes, Open Shift or with a serverless framework like Knative or Code Engine or on other platforms, it is helpful to pass endpoints to other applications to the containerized application by using environment variables. When the container will be restarted, these variables can be provided to the container and no adjustment in the source code is necessary. You can use configmaps or in Code Engine simple the environment variable itself.