[ADD] discuss: Get organized by planning activities

Original doc: https://docs.google.com/document/d/1vWO0A5FqKItFgRq3QM-t-enXyD1h5MFRxdoXjyHi6yg/edit

discuss.rst

@@ -12,5 +12,6 @@ Discuss
    discuss/monitoring
    discuss/mentions
    discuss/team_communication
+   discuss/plan_activities
    discuss/mail_twitter
    discuss/email_servers

discuss/plan_activities.rst

@@ -0,0 +1,38 @@
+====================================
+Get organized by planning activities
+====================================
+
+Planning activities is the perfect way to keep on track with your work.
+Get reminded of what needs to be done and schedule the next activities
+to undertake.
+
+Your activities are available wherever you are in Odoo. It is easy to
+manage your priorities.
+
+.. image:: media/plan_activities01.png
+    :align: center
+
+Activities can be planned and managed from the chatters or in the kanban
+views. Here is an example for opportunities :
+
+.. image:: media/plan_activities02.png
+    :align: center
+
+Set your activity types
+=======================
+
+A number of generic activities types are available by default in Odoo
+(e.g. call, email, meeting, etc.). If you would like to set new ones, go
+to :menuselection:`Settings --> General settings --> Activity types`.
+
+Schedule meetings
+=================
+
+Activities are planned for specific days. If you need to set hours, go
+with the *Meeting* activity type. When scheduling one, the calendar
+will simply open to let you select a time slot.
+
+.. tip::
+    If you need to use other activity types with a calendar
+    planning, make sure their *Category* is set as *Meeting*.
+