[IMP]l10n_ar_ux:prevent currency change when the invoice is not draft

closes #615

Ticket: 51808
Related: ingadhoc/account-financial-tools#341
Signed-off-by: Katherine Zaoral <kz@adhoc.com.ar>

l10n_ar_ux/wizards/account_move_change_rate.py

@@ -3,6 +3,7 @@
 # directory
 ##############################################################################
 from odoo import fields, models, api, _
+from odoo.exceptions import ValidationError
 
 
 class AccountMoveChangeRate(models.TransientModel):
@@ -26,6 +27,13 @@ def get_move(self):
         default=get_move
     )
 
+    @api.constrains('currency_rate')
+    def _prevent_change_currency(self):
+        """prevent currency change when the invoice is not draft
+        """
+        if self.move_id.state != 'draft':
+            raise ValidationError(_('This invoice is not draft, reset it to draft to change currency rate'))
+
     @api.onchange('move_id')
     def _onchange_move(self):
         self.currency_rate = self.move_id.l10n_ar_currency_rate or self.move_id.computed_currency_rate