[Koha] Patron Category TYPES

I already know that the Patron Category Types are hardcoded in the system. But is there a way for me to edit the code, for me to be able to add and delete category types? Because in our library, the Adult and Child Category types are not really useful. So we are planning to add the following category types: 1. Student (does need guarantor) 2. Employee (replacement to the Staff Category type) So we really need a way to edit the code and add the said category types. PLease help. Thanks in advance! Have a nice day.