[REF] l10n_au_keypay: remove au dependency

Keypay, now called Employment Hero, is not limited to Australia
but also supports Singapore, Malaysia,...

This task will:
- remove dependencies to Australia, to make it usable with other
localisation.
- Rename the module and all references to keypay and au in order to
keep the module clean for future use.
- Implement better error messages when the api returns one.
- Render the api key, and url company specific to support using
two different API on two separate companies.

Task id # 2925767

closes odoo/documentation#7276

Related: odoo/enterprise#53685
Related: odoo/upgrade#5494
Signed-off-by: Nicolas Viseur (vin) <vin@odoo.com>

content/applications/finance/fiscal_localizations/new_zealand.rst

@@ -0,0 +1,15 @@
+===========
+New Zealand
+===========
+
+.. _new-zealand/employment-hero:
+
+Employment Hero payroll
+=======================
+
+If your business is already up and running with :doc:`Employment Hero <employment_hero>`, you can
+use our connector as an alternative payroll solution.
+
+.. important::
+   To :ref:`configure the Employment Hero API <employment_hero/configuration>` for **New Zealand**,
+   use the following value as :guilabel:`Payroll URL`: `https://api.nzpayroll.co.nz/`.