docs/files.rst: added note about null ownership

docs/admin.rst

@@ -23,6 +23,8 @@ Currently, server settings are represented by the following object:
         "default_permissions": ["PERMISSION1", "PERMISSION2"]
     }
 
+.. _admin_anon_perms:
+
 Anonymous permissions
 ^^^^^^^^^^^^^^^^^^^^^
 

docs/files.rst

@@ -64,6 +64,11 @@ In JSON, a file share has the following properties::
       - Read-only
       - UUID that uniquely identifies this share.
 
+.. note::
+
+   Share ownership can be changed by changing ``owner_name``.
+   Do note that setting it to ``null`` is equivalent to :ref:`unauthenticated users<admin_anon_perms>` owning the share.
+
 .. _files_metadata_api:
 
 Metadata API