Persist Product & Plan in URL Flows

🔍 Problem Statement

Currently, when using URL triggers with a preselected product and plan, the selected product/plan is not consistently displayed throughout the subscription flow.

This issue occurs in flows that skip directly to registration, address, login, or payment steps using URL parameters such as:

1. ?view=plan-select&product_id=X&plan_id=Y

2. ?view=plan-select&product_id=X&plan_id=Y&is_gift=true

As a result, users may lose visibility of the selected product/plan during checkout.

💡 User Story

As a user accessing a subscription flow through a URL trigger with a predefined product and plan,

I want the selected product and plan information to remain visible throughout the entire flow,

so that I always know what I am subscribing to before completing checkout.

🎯 Definition of Done (DoD)

A feature is done when:

✔ Given a URL trigger containing product_id and plan_id,

when the user enters the subscription flow,

then the selected product and plan are preserved and displayed across all steps.

✔ The selected product/plan is shown in:

1. Login modal

2. Create account modal

3. Address modal

4. Payment modal

✔ Gift flows using is_gift=true also preserve and display the selected product/plan information.

✔ The current “preselected product” component is enhanced to also display the selected plan name when plan_id exists in the URL.

1. Any flows using product/plan URL triggers should be covered

✔ Product and plan information remains consistent even when the flow skips directly to later checkout steps.