Create the following models:
A Doctor model, which has the following attributes:
- a first_name, which is a string
- a last_name, which is a string
- a specialty, which is a string
- a zip_code, which is a string
A Patient model, which has the following attributes:
- a first_name, which is a string
- a last_name, which is a string
An Appointment model, which has the following attribute:
- a date, which is a datetime.
Then, create data through the seed.db file