The deploy.yaml deploys a Doccano environment, which is a popular annotation tool for data scientists today. More specifically, the deploy.yaml specifies the https://hub.docker.com/r/doccano/doccano which is the official doccano image.
Once deployed, Doccano can be accessed at http:<HOSTED URI>:<REDIRECTED_PORT>. The ADMIN_USERNAME and ADMIN_PASSWORD are set in the deploy.yaml file. By default, the admin username is 'admin' and the password is 'passowrd'.
For more information about management of user, please visit the official documentation at https://doccano.github.io/doccano/.