This update adjusts Belgian payroll settings to reflect current employer social contribution rates and revised default allowances. It also changes how commissions are paid and adds a clearer, rule-based reimbursement option for employees commuting by private car.

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When a salesperson creates a quotation from an opportunity without a customer, Odoo now asks whether to create a new customer from the opportunity details or select an existing one. This prevents quotations from being created without customer information and keeps the opportunity and quotation aligned.

When creating a quotation from a opportunity that does not have any 
customer set, we ended up on a quotation without any customer or any of 
the contact information entered on the crm.lead.

With this commit, if no customer is set on the opportunity, when hitting New 
Quotation button,  a modal is displayed to ask the user what to do to fill in the 
customer field.

- Create a new customer : Use the information from the opportunity to create 
automatically a res.partner. Set the res.partner on the quotation 
and on the opportunity.
- Use an existing customer : Set this customer on the quotation 
and on the opportunity.

Extra
For consistency, in the 'convert to opportunity' modal, 
move the 'create a new customer' at the top of the selection values
+ change the group title to 'Customer' instead of 'Customers'

Task-1917332

The salary configurator now presents clearer choices for phone subscriptions, including international communication as part of the highest plan. It also aligns commission plan handling with related payroll changes and updates commuting options by adding private car while removing the generic other option.

Belgian payroll contracts can now set a voluntary higher withholding tax rate, helping employees spread tax payments across the year instead of facing a larger year-end bill. Payslip reporting is also improved with clearer fleet vehicle information, including license plate display.