Create one invoice for customers with multiple plans/subscriptions.

🔍 Problem Statement

Customers with multiple subscriptions receive a separate invoice for each one. This creates a cluttered billing experience and complicates payment processing for both the customer and the admin — especially for organisations with many active plans.

💡 User Story

As a Pelcro admin, I want the ability to consolidate multiple subscriptions into a single invoice per billing cycle, so that customers receive one clear bill and payment processing is simplified.

🎯 Definition of Done (DoD)

A feature is done when:

✔️ Given a customer with multiple active subscriptions, when the billing cycle runs, then all eligible subscriptions are grouped into a single consolidated invoice — and the invoice clearly itemises each subscription.