bug fix, root user

[tm-sanjay]

MYSQL_USER: "root" this will cause an issue.
[ERROR] [Entrypoint]: MYSQL_USER="root", MYSQL_USER and MYSQL_PASSWORD are for configuring a regular user and cannot be used for the root user

the root will be automatically created https://stackoverflow.com/a/66910240/13577765

[ur2e]

• docker-entrypoint.sh

if [ "$MYSQL_USER" = 'root' ]; then
                mysql_error <<-'EOF'
                        MYSQL_USER="root", MYSQL_USER and MYSQL_PASSWORD are for configuring a regular user and cannot be used for the root user
                            Remove MYSQL_USER="root" and use one of the following to control the root user password:
                            - MYSQL_ROOT_PASSWORD
                            - MYSQL_ALLOW_EMPTY_PASSWORD
                            - MYSQL_RANDOM_ROOT_PASSWORD
                EOF
fi

docker-library/mysql#750 (comment)