class diagram: https://lucid.app/lucidchart/d339a4fd-e139-4ccf-aef2-8e3e283b4104/edit?invitationId=inv_d1d1d200-4ee4-44af-9a70-4019f0e9bdac&page=0_0#

notion: https://yunjeongiya.notion.site/1102fac8f26980afafece7003015b18a?v=e16580f916a14dbaa0beb82cddf993a5&pvs=4