mrp_p_auto_validate: fix auto_validate flag

Relying on onchange makes this value set only if the BOM is set
manually on the Form view, what isn't the case when MO are created
by running procurements.

mrp_production_auto_validate/models/mrp_production.py

@@ -13,7 +13,9 @@ class MrpProduction(models.Model):
 
     auto_validate = fields.Boolean(
         string="Auto Validate",
-        default=False,
+        compute="_compute_auto_validate",
+        store=True,
+        states={"draft": [("readonly", False)]},
     )
 
     @api.constrains("bom_id", "auto_validate", "product_qty")
@@ -39,11 +41,16 @@ class MrpProduction(models.Model):
                     ).format(qty=mo.bom_id.product_qty)
                 )
 
-    @api.onchange("bom_id")
-    def _onchange_bom_id(self):
-        res = super()._onchange_bom_id()
-        self.auto_validate = self.bom_id.mo_auto_validation
-        return res
+    @api.depends("bom_id.mo_auto_validation", "state")
+    def _compute_auto_validate(self):
+        for prod in self:
+            if prod.state != "draft":
+                # Avoid recomputing the value once the MO is confirmed.
+                # e.g. if the value changes on the BOM but the MO was already confirmed,
+                # or if the user forces another value while the MO is in draft,
+                # we don't want to change the value after confirmation.
+                continue
+            prod.auto_validate = prod.bom_id.mo_auto_validation
 
     def _auto_validate_after_picking(self):
         self.ensure_one()