Stripe Create Customer - update docs

[PandyLegend]

I am using the Payum Bundle and Stripe.
I want to be able to save a card for future use but I think the docs are out-of-date as I believe you need to create/link a customer when saving a card. It certainly doesn't work when coded as described.

How should this be implemented? I note that there is a CreateCustomerAction available but I can find no examples anywhere of how this should be used, either for saving a card or creating a subscription.

Can you provide an example here and also update the docs?

I think this may be related to issue #909 as well.