[ADD] inventory: How to configure and run schedulers?

https://docs.google.com/document/d/1DkJEPJFHsvuCxOBYfRczIzIOdMh7bRNIrvTTReSNHLE/edit#heading=h.n2iytrp9tz2x

inventory/misc/schedulers.rst

@@ -1,3 +1,63 @@
 ====================================
 How to configure and run schedulers?
 ====================================
+
+What is a scheduler
+===================
+
+The scheduler is the calculation engine which plans and prioritises
+production and purchasing automatically according to the rules defined
+on products. By default, the scheduler is set to run once a day (Odoo
+automatically creates a **Scheduled Action** for this).
+
+Calculating Requirements / Scheduling
+-------------------------------------
+
+Scheduling only validates procurements that are confirmed but not yet
+started. These procurement reservations will themselves start
+production, tasks or purchases depending on the configuration of the
+requested product.
+
+You take into account the priority of operations when starting
+reservations and procurements. Urgent requests, those with a date in the
+past, or requests with a date earlier than the others will be started
+first. In case there are not enough products in stock to satisfy all the
+requests, you can be sure that the most urgent requests will be produced
+first.
+
+Configure and run the scheduler
+===============================
+
+Run the scheduler manually
+--------------------------
+
+This feature is not visible by default. You have to enable **debug mode** to
+see this. To enable debug mode, go to :menuselection:`Help --> About` and click on
+**Activate the developer mode**.
+
+You can also start the scheduler manually from the menu 
+:menuselection:`Inventory --> Schedulers --> Run Schedulers`. The scheduler 
+uses all the relevant parameters defined for products, suppliers 
+and the company to determine the priorities between the different 
+production orders, deliveries and supplier purchases.
+
+.. image:: media/schedulers02.png
+   :align: center
+
+Configure and run the scheduler (only for advanced users)
+---------------------------------------------------------
+
+This feature is not visible by default. You have to enable **debug mode** to
+see this. To enable debug mode, go to :menuselection:`Help -> About` and click on
+**Activate the developer mode**.
+
+You can set the starting time of the scheduler by modifying the
+corresponding action in the menu 
+:menuselection:`Settings --> Technical --> Automation --> Scheduled Actions`. 
+Modify the Run mrp Scheduler configuration.
+
+.. image:: media/schedulers01.png
+   :align: center
+
+.. seealso::
+    * :doc:`../delivery/scheduled_dates`