[FIX] account: allow creating move in branch without parent access

When a user only has access to a branch and not to the parent, he can
not create a new customer invoice or vendor bill, since we need to check
the lock date on all ancestor companies (where the user might not have
access to).

This fix allows the user to create a new customer invoice or vendor bill
again when only having access to a branch.

Furthermore, in the above case we are also unable to assign a partner on
the invoice/bill, since we are checking properties that might belong to
an ancestor company we don't have access to. We also fixed that here, so
a partner can be selected.

task-3503204

Part-of: odoo/odoo#138942

addons/account/models/account_move.py

@@ -1737,7 +1737,7 @@ class AccountMove(models.Model):
 
     @api.onchange('partner_id')
     def _onchange_partner_id(self):
-        self = self.with_company(self.journal_id.company_id)
+        self = self.with_company(self.journal_id.company_id._accessible_branches()[:1])
 
         warning = {}
         if self.partner_id:

addons/account/models/company.py

@@ -356,7 +356,8 @@ class ResCompany(models.Model):
         if self.user_has_groups('account.group_account_manager'):
             lock_date = self.fiscalyear_lock_date or date.min
         if self.parent_id:
-            lock_date = max(lock_date, self.parent_id._get_user_fiscal_lock_date())
+            # We need to use sudo, since we might not have access to a parent company.
+            lock_date = max(lock_date, self.sudo().parent_id._get_user_fiscal_lock_date())
         return lock_date
 
     def _get_violated_lock_dates(self, accounting_date, has_tax):