Spike: Determine Unified Purchase Flow Transition Strategy

Purpose

This spike aims to define the transition strategy for unified purchase flow.

Objective

Investigate and evaluate the approach of creating a new controller and endpoint (Subscriptions::PurchaseController#new) which SubscriptionsController#new will redirect to as a temporary transition mechanism for the unified purchase flow.

We should consider the existing logic in SubscriptionsController (particularly before_action hooks) and figure out the best place to branch to the new UI.

We should also look into defining an approach to pass data that the UI relies on in a generic way so we can achieve a less hands on approach when offering new products, e.g. plan, plans, namespace, namespaces, subscription etc.

Result

• Transition strategy for unified purchase flow is defined
• High level task breakdown is updated with any additional work
• Level of effort is estimated and added to LoE in #11461 (closed)