Bubble.io auth process

I’m going to create a bubble.io app but this is what need help with

- when signing into the bubble app I need to
- make a call to my external api
- it’s a POST with Json load in body
- then my api sends back access token
- that access token is custom to the user
- that access token needs to be used in ever api call
- my api will be used as the database to the app

Is this possible and can you help ?