old_contents: # -*- coding: utf-8 -*-
  # © 2011 Akretion Sébastien BEAU <sebastien.beau@akretion.com>
  # © 2013 Camptocamp SA (author: Guewen Baconnier)
  # © 2016 Sodexis
  # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
  
  from odoo import models, fields
  
  
  class AccountInvoice(models.Model):
      _inherit = "account.invoice"
  
      workflow_process_id = fields.Many2one(
          comodel_name='sale.workflow.process',
          string='Sale Workflow Process'
      )
  
new_contents: # -*- coding: utf-8 -*-
  # © 2011 Akretion Sébastien BEAU <sebastien.beau@akretion.com>
  # © 2013 Camptocamp SA (author: Guewen Baconnier)
  # © 2016 Sodexis
  # License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
  from odoo import models, fields
  
  
  class AccountInvoice(models.Model):
      _inherit = "account.invoice"
  
      workflow_process_id = fields.Many2one(
          comodel_name='sale.workflow.process',
          string='Sale Workflow Process',
          copy=False,
      )
  
subject: Fix issue on account.invoice about workflow_process_id: if a user duplicate an invoice, it copy also the workflow and validations (the reason of bugs)