This affects most tests in the package org/hibernate/test/annotations/derivedidentities when running with DB2

The tests need two adjustments:
- all primary key columns in derived entities need to be declared non-null, because db2 requires primary key components to explicitly be non-null
- if Employee.firstName and PolicyId.type are left to their default size (255) then db2 complains that it can't handle such long primary keys:

    07:55:18,511 ERROR SchemaExport:426 - HHH000389: Unsuccessful: create table Policy (type varchar(255) not null, dep_emp_firstName varchar(255) not null, dep_emp_lastName varchar(255) not null, dep_name varchar(255) not null, primary key (dep_emp_firstName, dep_emp_lastName, dep_name, type))
    07:55:18,511 ERROR SchemaExport:427 - DB2 SQL Error: SQLCODE=-613, SQLSTATE=54008, SQLERRMC=DEP_EMP_FIRSTNAME..., DRIVER=4.17.29

---> it works if these columns are trimmed to a smaller max. size, eg. 80