data transform and validation.

• 어떻게 검증할까?
  • class-validator lib
    • 어떤 level로 사용?
    • whitelist: any property not included in the whitelist is automatically stripped from the resulting object. (stripped property: this will automatically remove non-whitelisted properties (those without any decorator in the validation class)) → decorator있으면 whitelist
• 어떻게 dto와 entity를 map할까?
  • spread operator
  • Mapped types
    • Partial: make all fields optional.
    • Pick: constructs a new type (class) by picking a set of properties
    • Omit: removing a particular set of keys.
    • Intersection: combines two types into one new type (class).
    • Composition: all of the properties except for something, and those properties will be set to optional.