[FIX] website_sale: don't unlink website_description

This is a hotfix/hack for a conflict between website_sale and
website_quote, on the field website_description.
The conflict happens when both modules are installed.

Fixes #20118
Completes rev 333a236

addons/website_sale/models/__init__.py

@@ -4,3 +4,4 @@ import product
 import sale_order
 import crm_team
 import res_config
+import ir_model_fields

addons/website_sale/models/ir_model_fields.py

@@ -0,0 +1,35 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details.
+
+from odoo import api, models
+
+# !! Attention, this is a hack of a hack, do not try this at home !!
+# This is done because website_sale defines the website_description
+# field which is also defined by website_quote, but these two modules
+# are independent of each other, the part of the ORM that generates
+# xmlids does not support this case therefore it only creates a single
+# pair of xmlids for whichever module is installed first, therefore
+# when uninstalling any of the two modules the website_descripion field
+# will be deleted from the db and the other module won't be able to
+# use this field, resulting in a crash and data-loss.
+# See opw-776464 for more details.
+#
+# This is hotfixed by overriding the unlink method so as to not delete
+# the website_description field if website_sale is uninstalled, it's
+# an ugly hack but it works and big changes can't be done to the ORM
+# in stable versions, Odoo v12+ will properly fix this
+
+
+class IrModelFields(models.Model):
+    _inherit = "ir.model.fields"
+
+    @api.multi
+    def unlink(self):
+        # Prevent the deletion of the field "website_description"
+        self = self.filtered(
+            lambda rec: not (
+                rec.model in ('product.product', 'product.template') and
+                rec.name == 'website_description'
+            )
+        )
+        return super(IrModelFields, self).unlink()