Allow multiple frequencies of the same type to be added to Calendars and Schedules

Current Situation

• When creating Calendars or restrictions for Schedules then users can add frequencies such as "weekdays", "month days" etc. Any number of frequencies can be added, however, each frequency type can occur only once.
• Users would like to add the same frequency type any number of times.

Desired Behavior

• Users can add the same frequency type any number of times:
• Use cases include
  • to select separate days for each instance of the same frequency type.
  • to specify separate validity periods for each instance of the same frequency type.