Use final and readonly where possible

[derrabus]

Finalizing classes/methods or flagging properties as readonly helps a reader understand how a class is used and what impact a code change may have. I propose to make final and readonly the default in this codebase.

[SenseException]

Why are some classes "just" /** @final */?

[derrabus]

Because we create mocks for those classes. 😢

[SenseException]

I'm currently working on increasing the test coverage. I'll come back to the final-annotation in case a mock is serviceable. I don't want to use nunomaduro/mock-final-classes on new tests.

[derrabus]

Sure, whenever you need to create a mock, feel free to un-finalize classes.