Shouldn't need an end date for a sprint

I was going to make a sprint called "Good First Bugs" and put a bunch of them in there, but the end date is mandatory. Seems like for things like tech-debt or goodfirst bug we shouldn't have that.

(raises question if maybe that isn't for sprinter then....

No files or tests are identified. Start by tracing the sprint creation flow and locating where the end date becomes mandatory; done means the intended sprint types can be created without an end date, with tests covering that behavior.

Written by the indexing model from the issue text.