remind

type Params struct {
	// should be now() in most cases, but this field is useful for testing purposes
	Today    time.Time
	InNbDays int
	// when false, check birthdays which matches exactly Today + InNbDays
	// when true, check birthdays which matches every days between Today and Today + InNbDays
	Inclusive bool
}

type Reminder struct {
	Contacts     []contact.Contact
	RemindParams Params
}