add Instant default for config

[webecke]

Some silly goose me forgot to set up the default value of an Instant in the Configuration SQL dao. So that meant it would crash when starting up. This fixes that bug currently on the main branch that came from #466

Guess I need to do more thorough testing

[frozenfrank]

Looks good. Typescript has ways to protect against this kind of error, but is there a way to identify it at compile time with Java?

[ThanGerlek]

Not easily, it seems. The simplest way seems to be to simply overload all the relevant functions, which would let us get rid of that generic entirely, but that would mean modifying the ConfigurationDao interface and every relevant implementation whenever we add a new type. Or create wrapper classes for every type which also seems like a bit much.