The GSTR return period form now hides the tax unit option when no tax unit is available. This keeps the form cleaner and avoids showing users an irrelevant choice.

In this PR
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**[IMP] l10n_in_reports_gstr: hide tax unit if not available**
- This commits hides the tax unit for gstr return period form if no tax unit is available

task-3679488

The online sales templates for rentals and subscriptions were simplified after related product page caching was removed. This keeps the website sales experience aligned with platform changes and should make future maintenance easier without changing visible business workflows.

Now that the cache has been removed from product page, those templates (or part of) can be simplified.

See also:
https://github.com/odoo/odoo/pull/145532
https://github.com/odoo/upgrade/pull/5422