EES-6692: Add checklist warning when data upload missing association with API data set

[tomjonesdev]

This PR adds a warning message when a user has uploaded a data file when the publication has an API data set, but has not created a new version of said data set using that uploaded file.

The show/don't show logic covers a few cases; the publication has an API data set, and:

1. it's the first release in the publication (don't show)
2. a file has been uploaded, but not associated with the API data set (show)
3. no files have been uploaded (don't show)
4. a data upload has been associated with the API data set, but not yet mapped (don't show - there's an error instead)
5. all data uploads have been associated with an API data set (don't show).

The logic misses this case:

• viewing an already published release which should show the warning (i.e. it was published without handling the warning), will not currently show the warning. If a reviewer can see a simple solution to this please let me know, but the checklist isn't particularly relevant once published so it didn't seem worth spending too much extra time on this.

This PR also includes a class to separate checklist validation out to a service so that individual rules can be more easily tested. This has the added benefit of reducing the complexity of the checklist service, and I think moving the other methods out might be useful (suggest raising a new task if you agree).

I also added a checklist test for unresolved comments as this must have been missed from previous work.

[mmoalin]

Good approach, I haven't tested this nor been had any immediate thoughts pop up for the scenario that you mentioned which is to do with published releases, I just had some minor comments though.

[mmoalin]

Had checked out the branch and noticed a bug with the 'scheduled releases' status.