If I have a marketplace (something like RapidAPI or Shopify, for example), can I use Lago to allow my providers to create custom pricing plans for their customers? Skimming the Lago API, I see that I can create all the parts of custom pricing plans, but can I group/separate them as well? As in, can there be pricing plans for company A with coupons for A, but company B has their own plans and coupons? Is that something Lago supports, or at least something that I can accomplish with my business logic (ie. prefixing plans with A, B, etc) – or completely out of scope?
That's totally doable. You can simply create a price plan per customer, and call the subscriptions api to assign a plan to a customer. In addition to this, you can create a basic coupon, but override the value when assigning the coupon to a customer. Everything you described in your comment is totally doable with Lago API