This is an educational application for database system instructors. It allows an administrator to add connections to databases, create quizzes for particular queries, and then to test students' abilities to solve for the SQL on their own.
The credentials are encrypted and stored in the master database.
The environment variable APP_KEY holds the encryption key
which is initially generated by the php artisan key:generate command.
If the key is regenerated, then previously saved values cannot be decrypted.
If you backup and restore the database to a new server instance,
then the old APP_KEY will also be needed to decrypt those values.