[FIX] point_of_sale: default pricelist test

The POS js tests expect the "Public Pricelist" when
selecting a lambda customer in the pos interface.

Nevertheless, when installing a localization
with a specific currency,
other than the currency of the public pricelist,
it creates a new pricelist called
"Default %(currency)s pricelist for %(company)s"
and sets it by default for the customers sale pricelist.
See
https://github.com/odoo/odoo/commit/787e1037cdca48fe361ae65d790056a3d57e6b67#diff-840bfc6fc7a986fbf0e248c83d2ac1d5R57

Therefore, in the POS js tests, the pricelist selected
when selecting a lambda user was no longer
'public pricelist' but the one mentioned above,
and the tests therefore failed.

The issue is solved by creating a dedicated "Public Pricelist"
for the purpose of these tests, and sets it by default
for the customer sale pricelist,
as well as for the pos config default pricelist.

The test case was to install `l10n_pe` with `point_of_sale`
while activating the test.
e.g. `-i l10n_pe,point_of_sale --test-enable`

opw-1890928
opw-1910249

closes odoo/odoo#28839

addons/point_of_sale/tests/test_frontend.py

@@ -197,6 +197,10 @@ class TestUi(odoo.tests.HttpCase):
         one_week_from_now = today + timedelta(weeks=1)
         two_weeks_from_now = today + timedelta(weeks=2)
 
+        public_pricelist = env['product.pricelist'].create({
+            'name': 'Public Pricelist',
+        })
+
         env['product.pricelist'].create({
             'name': 'Dates',
             'item_ids': [(0, 0, {
@@ -283,9 +287,19 @@ class TestUi(odoo.tests.HttpCase):
                                                        'type': 'cash',
                                                        'company_id': main_company.id,
                                                        'journal_user': True})],
+            'pricelist_id': public_pricelist.id,
             'available_pricelist_ids': [(4, pricelist.id) for pricelist in all_pricelists],
         })
 
+        # Change the default sale pricelist of customers,
+        # so the js tests can expect deterministically this pricelist when selecting a customer.
+        field = env['ir.model.fields']._get('res.partner', 'property_product_pricelist')
+        env['ir.property'].search([
+            ('name', '=', 'property_product_pricelist'),
+            ('fields_id', '=', field.id),
+            ('res_id', '=', False)
+        ]).write({'value_reference': 'product.pricelist,%s' % public_pricelist.id})
+
         # open a session, the /pos/web controller will redirect to it
         main_pos_config.open_session_cb()