Adding time to duration doesn't create the same result as adding duration to time

[par-shd]

Describe the Bug

Addition of time and duration types should create a time type (See Camunda docs). If the first and second argument of addition are time and duration types, the result is as expected. But if the first and second argument of addition are duration and time (the reverse order of the previous situation), the result becomes a number.

Steps to Reproduce

See playground

Expected Behavior

If the first and second argument of addition are duration and time, the result should be a time.

[nikku]

Thanks for the report. The following should be all true:

[
  date("2020-04-06") + duration("P1D") = date("2020-04-07"),
  duration("P1D") + date("2020-04-06") = date("2020-04-07"),
  time("08:00:00") + duration("PT1H") = time("09:00:00"),
  duration("PT1H") + time("08:00:00") = time("09:00:00"),
  date and time("2020-04-06T08:00:00") + duration("P7D") = date and time("2020-04-13T08:00:00"),
  duration("P7D") + date and time("2020-04-06T08:00:00") = date and time("2020-04-13T08:00:00"),
  duration("P2D") + duration("P5D") = duration("P7D")
]

It seems like we don't handle duration + date/time appropriately. Happy to take a contribution that improves this.