This change centralizes the rule used to identify service-related sales order lines across planning, helpdesk, and field service areas. It reduces duplicated logic, helping keep behavior consistent and lowering the risk of future maintenance errors.

## Description
The domain that specifies a `sale.order.line` as a service is repetitive and always the same.
To avoid incoherence, refactoring it into a separate method.

## Reference
task-3747138