User.StoreFile: Store user files
================================

Implement this method:

.. function:: StoreFile(filename string, data []byte) (err error)

    - Stores the file persistently for future retrieval.

    - If a user calls StoreFile() on a filename that already exists, the content
      of the existing file is overwritten.

    :param filename: File name
    :type filename: string
    :param data: File contents
    :type data: []byte

.. warning::
    Do not forget that your design must satisfy **all** requirements, including:
    
    #. Different users can store files using the same filename because each user
       must have a separate file namespace (see :ref:`requirement_files` #6).

    #. Overwriting the contents of a file  does not change who the file is
       shared with (see :ref:`requirement_files` #8).

    #. Users can have multiple active user sessions at once (see
       :ref:`requirement_user_sessions`).