I have a customer that is logged into my application.
const customerId = '1234';
I want him to be able to add a card so he can use it later for purchasing items in my shop.
But theres many of possible requests and im not really sure which one should be used in such situation.
createSource();
createPaymentMethod();
createSetupIntent();
What is the proper way in Stripe to add a card by customer?
You'd use Setup Intents which will facilitate the authentication and saving of payment details to an existing Customer object. There's a guide here on how to achieve this.