Add a MySQL user account.
url: Connection url
username: Create a user with this user name.
password: Create a user having this password.
allowed-host: Allow the user to connect from host (e.g. 127.0.0.1, any, etc.)
--grant: Grant these privileges to the user
--grant-level: Grant the privileges ON this level (e.g. *.*, dbname.*, dbname.tablename, etc.)
--can-grant: Grant the user to grant other users own privileges
--check: Do not actually make any changes, but report whether or not a change would be made.