[IMP] mail: add activities allowing to define next actions on various models

This commit introduces generic activities to use in your addons. Activities are
actions user have to take on a document like making a phonecall or organizing
a meeting. Activities come with the mail module as they are integrated in the
Chatter but are not bundled with mail.thread.

New models are

 * mail.activity.type: used to categorize activities. Each type is a different
   kind of activity e.g. call, mail, meeting. An activity can be generic i.e.
   available for all models using activities; or specific to a model in which
   case res_model_id field should be used.
 * mail.activity: an actual activity to perform. Activities are linked to
   documents using res_id and res_model_id fields. Activities have a deadline
   that can be used in kanban view to display a status. Once done activities
   are unlinked and a message is posted. This message has a new activity_type_id
   field that indicates the activity linked to the message.

This commit introduces a mail.activity mixin to use in various addons that
enables the activities feature. It works like the mail.thread mixin. It defines
a activity_ids one2many field toward activities using res_id and res_model_id.
Various related / computed fields are also added to have a global status of
activities on documents.

Activities come with a new JS widget for the form view. It is integrated in the
Chatter widget although it is a separate widget. It displays activities linked
to the current record and allow to schedule, edit and mark done activities.
Use widget="mail_activity" on activity_ids field in form view to use it.

There is also a kanban widget defined. It defines a small widget to integrate
in kanban vignettes. It allow to manage activities directly from the kanban
view. Use widget="kanban_activity" on activitiy_ids field in kanban view to
use it.

Next commits will aim at integrating activities inside main Odoo addons.

Thanks to R&D India for their work and testing on this task. Thanks to belgian
Usabiliteam for reviewing and testing it. Thanks to @jem-odoo for the final
review. May his soul lie in peace with the trumpets of paradise.

1 files changed, 27 insertions, 0 deletions

diff --git a/addons/mail/data/mail_activity_data.xml b/addons/mail/data/mail_activity_data.xml
new file mode 100644
index 00000000000..8e9a213dcff
--- /dev/null
+++ b/addons/mail/data/mail_activity_data.xml
@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8"?>
+<odoo>
+    <data noupdate="1">
+        <record id="mail_activity_data_email" model="mail.activity.type">
+            <field name="name">Email</field>
+            <field name="icon">fa-envelope</field>
+            <field name="summary">Send an Email</field>
+        </record>
+        <record id="mail_activity_data_call" model="mail.activity.type">
+            <field name="name">Call</field>
+            <field name="icon">fa-phone</field>
+            <field name="summary">Make a Call</field>
+            <field name="days">2</field>
+        </record>
+        <record id="mail_activity_data_meeting" model="mail.activity.type">
+            <field name="name">Meeting</field>
+            <field name="icon">fa-users</field>
+            <field name="summary">Reminder for meeting</field>
+        </record>
+        <record id="mail_activity_data_todo" model="mail.activity.type">
+            <field name="name">Todo</field>
+            <field name="icon">fa-tasks</field>
+            <field name="summary">Task to perform</field>
+            <field name="days">5</field>
+        </record>
+    </data>
+</odoo>