MySql driver addChek() is not implemented

[bobonov]

Using addCheck() with Mysql driver throw and exception that "is not supported by MySQL"

It is supported CHECK constaint in create/alter table since

Mysql 8.0.16 https://dev.mysql.com/blog-archive/mysql-8-0-16-introducing-check-constraint/

and

MariaDB 10.2.1https://mariadb.com/kb/en/constraint/

In previous version, CHECK is ignored and do not generate an error.

Additional info

Q	A
Yii version	2.0.47
PHP version	7.4
Operating system	debian

[samdark]

Do you have time for a pull request?

[bobonov]

I think I can start to work on in a couple of weeks.