[FIX] mass_mailing: allow duplicating mailing contact from mailing list

Before this commit:
While trying to duplicate a mailing contact within particular
mailing list, it  throws an user error saysing that 'A mailing
contact cannot subscribe to the same mailing list multiple times.'

After this commit:
User can duplicate a mailing contact from a mailing list without
the user error. In this case, we simply remove the default_list_ids
from the context, because all the mailing lists will be simply be
copied over from the existing contact and so we don't have to
re-add the default ones.

closes odoo/odoo#66827

Task-id: 2431344
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/mass_mailing/models/mailing_contact.py

@@ -140,6 +140,15 @@ class MassMailingContact(models.Model):
 
         return super(MassMailingContact, self.with_context(default_list_ids=False)).create(vals_list)
 
+    @api.returns('self', lambda value: value.id)
+    def copy(self, default=None):
+        """ Cleans the default_list_ids while duplicating mailing contact in context of
+        a mailing list because we already have subscription lists copied over for newly
+        created contact, no need to add the ones from default_list_ids again """
+        if self.env.context.get('default_list_ids'):
+            self = self.with_context(default_list_ids=False)
+        return super().copy(default)
+
     @api.model
     def name_create(self, name):
         name, email = self.get_name_email(name)

addons/mass_mailing/tests/test_mailing_list.py

@@ -53,6 +53,18 @@ class TestMailingListMerge(MassMailCommon):
             new = new.with_context(default_list_ids=[list_id])
             self.assertFalse(any(contact.opt_out for contact in new))
 
+    @users('user_marketing')
+    def test_mailing_list_contact_copy_in_context_of_mailing_list(self):
+        MailingContact = self.env['mailing.contact']
+        contact_1 = MailingContact.create({
+            'name': 'Sam',
+            'email': 'gamgee@shire.com',
+            'subscription_list_ids': [(0, 0, {'list_id': self.mailing_list_3.id})],
+        })
+        # Copy the contact with default_list_ids in context, which should not raise anything
+        contact_2 = contact_1.with_context(default_list_ids=self.mailing_list_3.ids).copy()
+        self.assertEqual(contact_1.list_ids, contact_2.list_ids, 'Should copy the existing mailing list(s)')
+
     @users('user_marketing')
     def test_mailing_list_merge(self):
         # TEST CASE: Merge A,B into the existing mailing list C