Update the composer package

Signed-off-by: mariossotir <mai1211@uom.gr>
Install PHPUnit.

Signed-off-by: mariossotir <mai1211@uom.gr>
Set the type of the $client parameter at method "generate" of the
ClientIdGeneratorInterface interface.

Signed-off-by: mariossotir <mai1211@uom.gr>