api key for a phoenix application

i have to create a phoenix umbrella application for a school project and we have to implement a rest api using postman with users, and they can generate an api key with which they can perform the Rest operations with postman (the operations are getting, posting, updating and deleting cats) but im stuck because i dont know how to implement this.
Please add the Phoenix tag (as well as two other tags) when posting threads in this section. Thanks!