Privileged docker images write files with inappropriate UIDs and GIDs

If one mounts a host machine directory (e.g., `server/db_data`) into a docker container running privileged in a *rootless* docker, then one can get files created that the owning user on the host machine does not own, and cannot delete, causing failures to start:

error checking context: no permission to read from '/home/rpg/src/planning-as-a-service/server/db_data/#ib_16384_0.dblwr'.

That file's UID and GID are both 328532966 on the host machine, so I have to bug a sysadmin to delete them before I can restart, or do a really complicated hokey-pokey where I docker exec bash in the MySQL DB container and do the job there....

Is there some way I could set the `MYSQL_USER` in `env` to avoid this?