How do people manage their free/premium newsletter lists <> subscription status?

Hey!

I was curious, how do most people manage their newsletters when you have paid subscribers?

Say you have a free tier and paid tier newsletter, and you have a subscriber on the free tier and they upgrade to the paid tier. You would have the following flow:

1. subscriber signs up to free tier
2. subscriber upgrades to paid tier:
   a. subscriber enters their CC details to setup recurring subscription billing, probably using Stripe or PayPal?
   b. on success, subscriber is added to premium newsletter list and removed from free tier
3. subscriber decides to unsubscribe:
   a. billing is cancelled via Stripe/PayPal
   b. on success, subscriber is removed from premium newsletter list once their paid period has expired and then added back to the free tier.

Are my assumptions on the subscriber flow accurate?
Is there a platform that manages this already, or are people manually managing or handrolling their own solution?

Thanks!