The subscription module now reuses standard portal capabilities instead of maintaining separate custom code. This reduces duplication and should make customer portal behavior for subscriptions easier to maintain and more consistent with other Odoo documents.

Sale subscription didn't inherit from portal.mixin and had to implement from
scratch many functions that were already implemented in the portal mixin. This
PR focuses on adapting the subscription module to use the mixin functionalities

task-2512070

This work updates and standardizes internal documentation text across several Enterprise app areas. It is mostly automated cleanup, so it should not change day-to-day behavior but may make future maintenance and support work easier.

Enterprise side of odoo/odoo#74604.

Mostly autofixes (search and replace) for now so the fixes are not complete or correct.