[FIX] ir_fields: import many2one_reference fields

Since a many2one_reference is simply an int, we can defer
_str_to_many2one_reference to _str_to_integer.

Note that to really validate the integer, we need the model_field of the
field, which should be stored in the record's values.
To get this information, _extract_records would have to be modified.

For the reported use-case, it does not matter as the create of the
message record checks for the existence of the related record,
so the validation works as expected.

Better support for this type of fields would be to allow for
import/export of xml_ids, which would avoid the need for the model.

opw 2087353

closes odoo/odoo#39591

Signed-off-by: Xavier Morel (xmo) <xmo@odoo.com>

odoo/addons/base/models/ir_fields.py

@@ -416,6 +416,10 @@ class IrFieldsConverter(models.AbstractModel):
         id, _, w2 = self.db_id_for(model, field, subfield, record[subfield])
         return id, w1 + w2
 
+    @api.model
+    def _str_to_many2one_reference(self, model, field, value):
+        return self._str_to_integer(model, field, value)
+
     @api.model
     def _str_to_many2many(self, model, field, value):
         [record] = value