Regarding to classes that can/may be used for entities in room whith Kotlin,

1. Is it mandatory to use data classes? Or could I use 'normal classes', i.e., the ones I use for the 'bussiness logic'
2. In case data classes are mandatory: can I add functionality to what they have by default? i.e, can I add functions (for whatever taks they may need) to them?

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