fix: reorder a rotation in which a user participates more than once

[dctalbot]

• Identified the issue which this PR solves.
• Read the CONTRIBUTING document.
• Code builds clean without any errors or warnings.
• Added appropriate tests for any new functionality.
• All new and existing tests passed.
• Added comments in the code, where necessary.
• Ran make check to catch common errors. Fixed any that came up.

Description:
Fixes #1478

[mastercactapus]

Using an index causes subtle issues, especially w.r.t. keyboard use and focus:
https://github.com/atlassian/react-beautiful-dnd/blob/master/docs/guides/identifiers.md#avoid-reusing-ids

[dctalbot]

@mastercactapus good catch. I'm a bit stumped on what to do here. We could potentially expose rotation participant ID's from graphql. Any ideas?

[mastercactapus]

Yeah, I spent an hour or two last week trying to come up with something. Participant IDs wouldn't work either because we update those entries, rather than reorder them, in the backend. We'll need to persist reorder history or something and match it up to get stable IDs of some sort.

Maybe this would work:

• create a list of "ids" based on index
• hold the most recent reorder in state
• apply the recent reorder to the list of "ids"

I think it might work if we just handle the most recent action. That way we don't lose focus on the current element from it being replaced due to a key change.

[Forfold]

Works great! Just had the one thing about maintenance then it looks good to go. Crazy that this has been present for so long 🤯