[Compliance] Add tax reverse charge mode

[JustShah]

Description

This pull request introduces enhancements to the tax applicability logic and updates the admin interface to support the new functionality.

Changes:

1. Tax Applicability Logic:

   • Introduced the tax_applicable? method in the Spree::Tax::TaxHelpers module. This method determines if tax is applicable based on the tax_reverse_charge_mode of the tax category and the reverse_charge_status of the address. The rates_for_item method has been updated to use this new logic, ensuring that only applicable tax rates are selected.
   • The tax_applicable? method supports three modes:
     • strict: Tax applies if the address reverse_charge_status is not equal to enabled (reverse charge).
     • loose: Tax applies if the address reverse_charge_status is not equal to disabled.
     • disabled: Tax always applies.

2. Admin Interface Updates:

   • Updated the admin interface to allow users to select the tax_reverse_charge_mode when creating or editing tax categories. The permitted parameters in the TaxCategoriesController have been updated to include tax_reverse_charge_mode.
   • The admin views and components have been updated to display the tax_reverse_charge_mode in the tax categories index and form views. This ensures that users can easily manage and view the reverse charge mode for each tax category.

3. Model and Spec Updates:

   • Introduced the tax_reverse_charge_mode enum to the Spree::TaxCategory model, with values disabled, loose, and strict. This change includes a migration to add the tax_reverse_charge_mode column to the spree_tax_categories table, with a default value of 0 (disabled). Additionally, the English locale file has been updated to include translations for the new enum values.
   • The related specs have been updated to test the new enum values and ensure that the tax_reverse_charge_mode is correctly validated and applied.

The tax_reverse_charge_mode enum allows for more granular control over tax applicability based on the reverse charge status of an address. This enhancement improves the flexibility and accuracy of tax calculations by enabling different tax handling modes. The updates to the admin interface ensure that users can easily manage and view the reverse charge mode for each tax category, providing a better user experience.

[fthobe]

@JustShah I see some tests failing can you check?