CRUD implementation How to use methods:

• save(userObject), takes user object and saves it to the database, the id is adds automatically;
• find(enumerationOption, criterion), takes one of the enum options as the first parameter, these are: BY_ID, BY_NAME, BY_BIRTH, BY_EMAIL, and the second is Integer when searching by id or String otherwise. Returns the first occurrence of the searched criterion;
• findAll(), returns a list of users of the entire table;
• update(userObject), updates user object by id in the database. Before updating you need to find the existing userObject in the database, modify it and then update;
• delete(userObject), removes the appropriate user object entry from the database. Before removing you need to find the existing userObject in the database.