Give privilege to new created databases in MySQL
It is impossible to do this using permissions only .

The only way is to create a stored procedure as described here

If you want to avoid stored procedures, a workaround is:
GRANT ALL PRIVILEGES ONtestuser_%. * TO 'testuser'@'%'; (as suggested here); however, this has the problem that the users must then be very careful in naming their databases.

For example if user aaa creates database bbb_xyz, it can then be accessed exclusively by user bbb but not by user aaa.