[MOV] documentation structure reorganization

This commit aims to improve the documentation's navigability by
redefining some categories' purposes and titles.

There is a redirection rule for each documentation page moved.
This ensures that users won't have a 404 error message.

task-3217827

closes odoo/documentation#8061

Signed-off-by: Jonathan Castillo (jcs) <jcs@odoo.com>

content/applications/finance/accounting/payments/follow_up.rst

@@ -90,6 +90,6 @@ select all the reports you would like to process, click on the :guilabel:`Action
 select :guilabel:`Process follow-ups`.
 
 .. seealso::
-   - :doc:`../../../general/in_app_purchase`
-   - :doc:`../../../marketing/sms_marketing/pricing/pricing_and_faq`
+   - :doc:`/applications/essentials/in_app_purchase`
+   - :doc:`/applications/marketing/sms_marketing/pricing/pricing_and_faq`
    - :doc:`../customer_invoices/snailmail`

content/applications/finance/accounting/payments/online/install_portal_patch.rst

@@ -26,8 +26,8 @@ If you use Odoo on Odoo.com or Odoo.sh platform, your code is already up-to-date
 to the next step.
 
 If you use Odoo with an on-premise setup or through a partner, you must update your installation as
-detailed in :doc:`this documentation page </administration/maintain/update>`, or by contacting your
-integrating partner.
+detailed in :doc:`this documentation page </administration/on_premise/update>`, or by contacting
+your integrating partner.
 
 Update the list of available modules
 ====================================