KRACOEUS-7308: JPA work for budget

So, we do not map the Award Extension object in JPA but set the default value for the discriminator column to 'Award'. This sounds like it should work unless JPA requires that there be more than one child class annotated with a discriminator annotation when using joined inheritance. I do not know why it would put such a constraint though. But this does sound like a decent approach if it works. What do you think @leoherbie ?