feat(usermanual): Add out-of-office/absence message feature

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

user_manual/groupware/absence.rst

@@ -0,0 +1,14 @@
+.. _groupware-absence:
+
+==============================
+Setting out-of-office messages
+==============================
+
+If you are absent for vacation, sick leave or similar, you can add an out-of-office message in the **Absence** section of the **Availability** settings.
+
+The interface asks for the time of absence, a short and a long message. This data is used for the following purposes:
+
+1) Your user status will change to the short message when your absence starts and reset when it ends.
+2) And event with status *busy* will be created in your personal calendar. This allows others to see that you are not available when they use the free/busy feature.
+3) If enabled, the Mail app will apply an autoresponder using the long message.
+4) The Talk app will show the long out-of-office message to others when they try to reach you in a 1:1 chat during your absence.

user_manual/groupware/calendar.rst

@@ -292,6 +292,8 @@ The general availability independent of scheduled events can be set in the group
 
 .. figure:: images/caldav_availability.png
 
+You can configure one-time absences on top of your regular availability in the :ref:`Absence settings section <groupware-absence>`.
+
 Birthday calendar
 -----------------
 

user_manual/groupware/index.rst

@@ -17,6 +17,7 @@ You can find out more about Nextcloud Groupware `on our website <https://nextclo
    contacts
    calendar
    mail
+   absence
    sync_android
    sync_ios
    sync_osx

user_manual/groupware/mail.rst

@@ -49,6 +49,8 @@ All inboxes
 ~~~~~~~~~~~~
 All messages from all the accounts you have logged in, will be shown here chronologically.
 
+.. _mail-account-settings:
+
 Account settings
 ~~~~~~~~~~~~~~~~
 Your account settings such as:
@@ -237,3 +239,16 @@ Snoozing a message or thread moves it into a dedicated mailbox until the selecte
 1. Open action menu of an envelope or thread
 2. Click *Snooze*
 3. Select how long the message or thread should be snoozed
+
+
+Filtering and autoresponder
+---------------------------
+
+The Mail app has a simple editor for Sieve scripts and an interface to configure autoresponders. Sieve has to be enabled in the :ref:`account settings <mail-account-settings>`.
+
+Autoresponders
+~~~~~~~~~~~~~~
+
+.. versionadded:: 3.5 Autoresponder can follow system settings.
+
+The autoresponder is off by default. It can be set manually, or follow the system settings. Following system settings means that the long absence message entered on the :ref:`Absence settings section <groupware-absence>` is applied automatically.