other interval types

[pyramation]

https://github.com/pyramation/pgtree/blob/master/nodes/intervals.go#L39-L68

[pyramation]

func (i IntervalModType) String() string {
	switch i {
	case Month:
		return "month"
	case Year:
		return "year"
	case Day:
		return "day"
	case Hour:
		return "hour"
	case Minute:
		return "minute"
	case Second:
		return "second"
	case Year | Month:
		return "year to month"
	case Hour | Day:
		return "day to hour"
	case Day | Hour | Minute:
		return "day to minute"
	case Day | Hour | Minute | Second:
		return "day to second"
	case Hour | Minute:
		return "hour to minute"
	case Hour | Minute | Second:
		return "hour to second"
	case Minute | Second:
		return "minute to second"
	}

	return ""
}