[FIX] payment: payment reference length
[FIX] payment: payment reference length

The payment reference of a S2S transaction has the given format:
'PAYMENT-9-170110_200204'. However, the reference is too long for some
providers such as Authorize (limited to 20 characters).

We make the reference less verbose as a first step to solve the issue.
However, case-by-case solutions will need to be found since the
reference depends on the id, which will ultimately grow.

opw-704615

hip-odoo/odoo,dfang/odoo,ygol/odoo,ygol/odoo,dfang/odoo,dfang/odoo,ygol/odoo,hip-odoo/odoo,ygol/odoo,dfang/odoo,hip-odoo/odoo,ygol/odoo,ygol/odoo,ygol/odoo,dfang/odoo,hip-odoo/odoo,hip-odoo/odoo,hip-odoo/odoo,dfang/odoo