[IMP]website_sale_installment_plans: Adds api constrainst to avoid divisor to be 0

[fw-bot-adhoc]

…visor to be 0

Forward-Port-Of: #404

[roboadhoc]

[fw-bot-adhoc]

@jov-adhoc @augusto-weiss cherrypicking of pull request #404 failed.

stdout:

CONFLICT (modify/delete): website_sale_installment_plans/models/account_card_installment.py deleted in 8f21327af1955d043a2e42f75f949282474200c4 and modified in 5904ae3d2b24fbf977ac205f061f43b3744cbe87.  Version 5904ae3d2b24fbf977ac205f061f43b3744cbe87 of website_sale_installment_plans/models/account_card_installment.py left in tree.

Either perform the forward-port manually (and push to this branch, proceeding as usual) or close this PR (maybe?).

In the former case, you may want to edit this PR message as well.

⚠️ after resolving this conflict, you will need to merge it via @roboadhoc.

More info at https://github.com/odoo/odoo/wiki/Mergebot#forward-port

[fw-bot-adhoc]

@jov-adhoc @augusto-weiss this forward port of #404 is awaiting action (not merged or closed).