documentation for user invoked ownership transfer

Signed-off-by: Sascha Wiswedel <sascha.wiswedel@nextcloud.com>

admin_manual/configuration_files/file_sharing_configuration.rst

@@ -73,6 +73,10 @@ Trashbin contents are not transferred::
  
 (See :doc:`../configuration_server/occ_command` for a complete ``occ`` 
 reference.) 
+
+Users may also transfer files or folders selectively by themselves.
+See `user documentation <https://docs.nextcloud.com/server/latest/user_manual/files/transfer_ownership.html>`_ for details.
+
    
 Creating persistent file Shares
 -------------------------------

admin_manual/configuration_server/occ_command.rst

@@ -724,6 +724,9 @@ It is also possible to transfer only one directory along with it's contents. Thi
 
  sudo -u www-data php occ files:transfer-ownership --path="path_to_dir" <source-user> <destination-user>
 
+Users may also transfer files or folders selectively by themselves.
+See `user documentation <https://docs.nextcloud.com/server/latest/user_manual/files/transfer_ownership.html>`_ for details.
+
 .. _files_external_label:
 
 Files external

user_manual/files/index.rst

@@ -17,4 +17,5 @@ Files & synchronization
    quota
    version_control
    projects
+   transfer_ownership
 

user_manual/files/transfer_ownership.rst

@@ -0,0 +1,25 @@
+========
+Transfer Ownership
+========
+
+Users can transfer the ownership of files and folders to other users. Share 
+ownerships of those transfered files/folders will also be transferred.
+
+#. Navigate to *Settings* > *Personal* > *Sharing* > *Files*
+#. Click on *Choose file or folder to transfer* >> A file picker opens, showing all files and folders in the user's account
+#. Pick a file or folder and click on *Choose* >> The chosen file or folder name gets displayed
+#. Click on *Change* to change the choice if necessary
+#. Pick a new owner by typing their name into the search field next to *New owner*
+#. Click on *Transfer*
+
+	.. note:: The username autocompletion or listing may be limited due to administrative visibility configuration.
+	   See `admin documentation <https://docs.nextcloud.com/server/latest/admin_manual/configuration_files/file_sharing_configuration.html>`_ for details.
+
+#. The target user receives a notification where they are being asked whether to
+   accept or reject the incoming transfer.
+
+	.. figure:: ../images/transfer_ownership-accept.png
+
+#. If accepted, the target user finds the transferred files and folders in their 
+   root under a folder *Transferred from [user] on [timestamp]*
+#. The source user gets informed about the acceptance or rejection by a notification