Fullstack Invoice app

Hi everyone, I would love to have some feedback about some optimizations that can be made on my code and some help with the validation and how to add the custom validity messages for evety imput, I have tried with the onInvalid event and setting an state variable that is true when the Invoice is save as pending so it can-t be saved without filling all the fields, but this was just adding validation just for the first input and even thought when everithing was filled was firing the Invalid event, Thank You.