add all api to sort by month

Sources/App/Libraries/SwiftDate/TimePeriod/TimePeriod+Support.swift

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+//
+//  SwiftDate
+//  Parse, validate, manipulate, and display dates, time and timezones in Swift
+//
+//  Created by Daniele Margutti
+//   - Web: https://www.danielemargutti.com
+//   - Twitter: https://twitter.com/danielemargutti
+//   - Mail: hello@danielemargutti.com
+//
+//  Copyright © 2019 Daniele Margutti. Licensed under MIT License.
+//
+
+import Foundation
+
+/// There may come a need, say when you are making a scheduling app, when
+/// it might be good to know how two time periods relate to one another
+/// Are they the same? Is one inside of another?
+/// All these questions may be asked using the relationship method of TimePeriod.
+public enum TimePeriodRelation {
+	case after
+	case startTouching
+	case startInside
+	case insideStartTouching
+	case enclosingStartTouching
+	case enclosing
+	case enclosingEndTouching
+	case exactMatch
+	case inside
+	case insideEndTouching
+	case endInside
+	case endTouching
+	case before
+	case none
+}
+
+/// Whether the time period is Open or Closed
+///
+/// - open: The boundary moment of time is included in calculations.
+/// - closed: The boundary moment of time represents a boundary value which is excluded in regard to calculations.
+public enum IntervalType {
+	case open
+	case closed
+}
+
+/// When a time periods is lengthened or shortened, it does so anchoring one date
+/// of the time period and then changing the other one. There is also an option to
+/// anchor the centerpoint of the time period, changing both the start and end dates.
+public enum TimePeriodAnchor {
+	case beginning
+	case center
+	case end
+}