[Feature]: Integrate customer ledger mechanism into the Invoicing plug-in for WooShop

[PapLabros]

Describe the solution you'd like

This issue proposes integrating a customer ledger mechanism into the Invoicing plug-in, similar to the one already implemented in the StoreBuddy application, so it can be utilized by the WooShop application.

Currently, WooShop relies on the Invoicing plug-in but lacks access to a customer ledger mechanism, which limits visibility into customer balances, charges, and payments. By adding this capability to the Invoicing plug-in, WooShop will gain access to ledger functionality without needing the full StoreBuddy feature set.

The implementation should follow the same conceptual model as StoreBuddy’s ledger mechanism, but it does not need to include all advanced features, since StoreBuddy already provides a richer, built-in version. The goal is to provide core ledger functionality required by WooShop while keeping the plug-in lightweight and focused.

Alternatives you've considered

No response

Additional context

No response