[12.0][IMP] - Different payment mode for contracts generated from sale orders

new option allow to set different payment mode for the contracts generated from
the sale order than the one will be used for invoices.

contract_sale_payment_mode/models/res_config_settings.py

@@ -0,0 +1,15 @@
+# Copyright 2020 ACSONE SA/NV
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+
+from odoo import fields, models
+
+
+class ResConfigSettings(models.TransientModel):
+
+    _inherit = 'res.config.settings'
+
+    specific_contract_payment_mode = fields.Boolean(
+        related="company_id.specific_contract_payment_mode",
+        string="Specific payment mode for contracts created from sale orders",
+        readonly=False
+    )