CE-1920: Use GitLab secrets for license key
It does not seem possible to store the MUI pro license key in the environment running the container, it must be built directly into the image.
See https://medium.com/swlh/reactjs-docker-environment-variables-f35eb591683e or https://stackoverflow.com/questions/52103155/reading-an-environment-variable-in-react-which-was-set-by-docker for examples.