-Evala button listeners stis klaseis createPet , createCustomers ,
customers : Anavathmish leitourgikothtas

- Ekana kapoies aparaithtes allages stous constructors twn klasewn pet
kai customer

- Prosthesa epipleon idiothta sth klassh Customers

- Plhrhs syndesh klasew customers - createAcustomer
PROSOXH! DEN KATAFERA NA SYNDESW TIS KLASEIS CREATE CUSTOMER - COSTUMERS
AMA H PRWTH DEN EINAI YPOKLASSH THS DEYTERHS (Dhmiourgia antigrafou
klasshs CreateCustomer  -> CreateCustomer_Beta)