Specify Host for User in docker compose file

I’ve started messing with Docker and the MySQL 5.7 image, and have created a docker-compose.yaml file to quickly bring up a DB instance with the root password set, a new user & password created, and a new database. When I log in to the new DB, I see that the new user is set with a host of %. I would like to be able to set this to a host of my choice in the yaml, but I can’t find any docs or notes on what environmental variable to specify in the docker-compose file.

Thoughts about how to accomplish this? I did attempt to set MYSQL_USER: dbadmin@host but this just created the user as dbadmin@host with the host still set to % in MySQL.