Hello, I will like to add a new field to the Point of Sale in Odoo 12, more specific the web one. (/pos/web)
I have managed to successfully display my field in the form, but when saving it does not retain the information, it is worth mentioning that I have not touched any JS function, only the .xml.

Here's what my code in the .xml looks like:
<selectclass='detail client-fiscal needsclick'name='property_account_position_id'><tt-foreach='widget.pos.fiscal_positions't-as='fiscal'><optiont-att-value='fiscal.id't-att-selected="partner.property_account_position_id ? (fiscal.id === partner.property_account_position_id[0] ? true : undefined) : undefined"><tt-esc='fiscal.name'/>option>t>select>

It doesn't work like this, it says that 'partner' is not define, but it works when name=" " but then don't safe the record, so I would really appreciate if someone tell me where I am wrong or wich JS or python function I have to modify.

Ty for your team and hope you have a great day