Add recommendation on using OAuth and app passwords (#49)

* Add recommendation on using OAuth and app passwords

* Update text

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Co-authored-by: Ricki Hirner <[email protected]>

Author: sunkup

introduction.rst

@@ -36,13 +36,20 @@ How to start using DAVx⁵ on your Android device:
 #. Open DAVx⁵.
 #. Follow the instructions of the start screen (permissions, battery saving etc.).
 #. Tap on "⊕ Add account" to add a new account.
-#. Enter your base URL / email address and login credentials.
+#. Login using provider-specific login (preferred if supported) or base URL / email address and login credentials.
    You can get the base URL from your service provider and/or our `list of tested services <https://www.davx5.com/tested-with/>`_.
 #. Finish the steps to add the account.
 #. Select the address books and calendars/task lists you want to synchronize so that the respective switches are enabled.
 #. Force sync ("🗘 Synchronize") if you want the data to be available immediately.
 #. Access your address books, events and tasks using your favorite apps (Contacts, Calendar, OpenTasks, …).
 
+If there's no provider-specific login for your provider, we recommend using an :abbr:`app password
+(server-generated random password that is only intended for a specific client and that can be used as a password substitute)`
+for DAVx⁵ (if supported by the server). To do so, open the Web interface of your service, go to authentication settings and
+look for something like *Create app password*. You can then use the app password instead of your account password in DAVx⁵.
+**Using a dedicated app password for each app — like DAVx⁵ — keeps your account password private and allows you to
+revoke access at any time.**
+
 When you create a contact/event, select the desired DAVx⁵ account as storage location.
 Local contacts/events will stay on your phone and not be synchronized. If you're using DAVx⁵ the first time, you may
 want to :faq:`transfer your local contacts to the CardDAV server <existing-contacts-are-not-synced>`.

settings.rst

@@ -86,6 +86,8 @@ Authentication
 User name / password / client certificate
   You can change the credentials used for synchronization at any time here (for instance, when your password has been changed on the server).
 
+  This option is not available when the account uses OAuth for authentication (provider-specific login).
+
 CalDAV
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