[MIG] account_partner_account_number: migrate to 18.0

account_partner_account_number/models/res_partner.py

@@ -0,0 +1,13 @@
+from odoo import fields, models, _
+
+
+class ResPartner(models.Model):
+    _inherit = "res.partner"
+
+    account_code = fields.Char('Account code')
+
+    _sql_constraints = [
+        ('account_coder_unique', 
+        'unique(account_code)',
+        'Choose another value of account code - it has to be unique!')
+    ]