code: func RegisterCallbacks(db *gorm.DB) {
  	if db.Callback().Create().Get("media:save_and_crop") == nil {
  		db.Callback().Create().After("gorm:after_create").Register("media:save_and_crop", saveAndCropImage(true))
  	}
  	if db.Callback().Update().Get("media:save_and_crop") == nil {
  		db.Callback().Update().Before("gorm:before_update").Register("media:save_and_crop", saveAndCropImage(false))
  	}
  }
docs: // RegisterCallbacks register callback into GORM DB