def index_group_key(name):
    """
    Return key for group_by. A-Z for alpha including Umlauts,
    0 for numbers and * for other.
    """
    if not name:
        return '*'
    key = name[0]
    key = key.upper()
    if key.isnumeric():
        return '0'
    for char, replacement in [(u'Ä', 'A'), (u'Ü', 'U'), (u'Ö', 'O')]:
        if key == char:
            return replacement
    if key.isalpha():
        return key
    return '*'