[FIX] account: allow forcing company when fetching fpos

The code to fetch the fiscal position of a partner uses ACLs and
ir_rules to select the correct ones, but when calling the function
as admin, multi-company rules flight out the window.

By allowing to force a company in the context, we can get the fpos
as the admin from the pov of any company.

addons/account/models/partner.py

@@ -123,6 +123,8 @@ class AccountFiscalPosition(models.Model):
         if not country_id:
             return False
         base_domain = [('auto_apply', '=', True), ('vat_required', '=', vat_required)]
+        if self.env.context.get('force_company'):
+            base_domain.append(('company_id', '=', self.env.context.get('force_company')))
         null_state_dom = state_domain = [('state_ids', '=', False)]
         null_zip_dom = zip_domain = [('zip_from', '=', 0), ('zip_to', '=', 0)]
         null_country_dom = [('country_id', '=', False), ('country_group_id', '=', False)]