@startuml

entity "User" as user {
  id: int
  --
  * username: string
  name: string
  phone: string
  external_email: string
  first_created: date
  locked: boolean
  comment: string
}

entity "Purchase" as purchase {
  id: int
  --
  * _user_id_: int
  * amount_paid: number
  * date: date
  comment: string
}

entity "Disk Purchase" as disk_purchase {
  --
  * size_mb: int
}

entity "Membership Type" as membership_type {
  id: int
  --
  * name: string
  * price: number
  comment: string
}

entity "Membership Purchase" as membership_purchase {
  --
  * _membership_type_id_: int
}


user "1..1" -- "0..*" purchase : makes
disk_purchase --|> purchase
membership_purchase --|> purchase

membership_type "1..1" -- "0..*" membership_purchase : is


@enduml