[Bug]: MySQL datetime with precision fails with CURRENT_TIMESTAMP default #277

What happened?

On MySQL a datetime column with a fractional seconds precision and CURRENT_TIMESTAMP as the default can't be created:

$schema = $database->table('events')->getSchema();
$schema->primary('id');
$schema->datetime('created_at', 6)->defaultValue(AbstractColumn::DATETIME_NOW);
$schema->save();

`created_at` datetime (6) NOT NULL DEFAULT CURRENT_TIMESTAMP

SQLSTATE[42000]: 1067 Invalid default value for 'created_at'

MySQL requires the default to have the same precision as the column: DEFAULT CURRENT_TIMESTAMP(6). MySQLColumn renders DATETIME_NOW without it. The same happens with #[Column(type: 'datetime(6)')] on a field managed by CreatedAt / UpdatedAt from cycle/entity-behavior.

Reproduced on MySQL 8.0.37 with cycle/database 2.10.0 and 2.23.3.

Version

cycle/database 2.x, MySQL 8.0