[IMP]base: Unique barcode for customers.

If two customers have same barcode -
Current functionality : To select customer in POS, if we scan barcode, only the newly created customer will be selected.

To resolve this: Created the unique sql constraint for customer per company.
This commit is related to task# 1877329.

closes odoo/odoo#28316

addons/point_of_sale/models/res_partner.py

@@ -11,6 +11,11 @@ class ResPartner(models.Model):
         help="The number of point of sales orders related to this customer",
         groups="point_of_sale.group_pos_user",
     )
+    barcode = fields.Char(oldname='ean13', help="Use a barcode to identify this contact from the Point of Sale.", copy=False)
+
+    _sql_constraints = [
+        ('unique_barcode', 'unique(barcode, company_id)', 'This barcode is already assigned to another contact. Please make sure you assign a unique barcode to this contact.'),
+    ]
 
     def _compute_pos_order(self):
         partners_data = self.env['pos.order'].read_group([('partner_id', 'in', self.ids)], ['partner_id'], ['partner_id'])

addons/point_of_sale/views/res_partner_view.xml

@@ -15,6 +15,12 @@
                         <field string="POS Sales" name="pos_order_count" widget="statinfo"/>
                     </button>
                 </button>
+                <xpath expr="//group[@name='purchase']" position="after">
+                    <group string="Point Of Sale" name="point_of_sale">
+                        <field name="barcode"/>
+                    </group>
+                </xpath>
+
             </field>
         </record>
         <record id="view_partner_pos_kanban" model="ir.ui.view">