added tests and indexes to readers on reader_card_id and to books on identity

Signed-off-by: Alex Izotov <martinandrudy@gmail.com>
changed librarians from birthday:datetime to birth_date:date and added validation model tests for librarians

Signed-off-by: Alex Izotov <martinandrudy@gmail.com>
added secure password to librarian and tests

Signed-off-by: Alex Izotov <martinandrudy@gmail.com>