Support date fields in worksheets as start and end dates in custom roadmaps Merged

Goal: use t-shirt sizes to estimate the timeframe to complete each epic and show the start and end dates on a custom roadmap.

In a worksheet we:

• Convert the t-shirt size to a relative, pre-determined number of days (tiny = 7 days, small = 14 days etc).

• We then use the epic start date and the above calculation to determine the estimated due date.

The challenge is that the calculated due date is not available for selection as the "End date" in the custom roadmap "edit data" modal.