Harvests: harvest overlapping validations appears to be matching files from other harvests

[atruskie]

When harvesting we check if any files in the harvest overlap with each other.

https://github.com/QutEcoacoustics/baw-server/blob/8914eb958b1f6bef3285a593e4954408d205cbbd/app/models/harvest_item.rb#L137-L161

It appears that we're finding harvest items that belong to other harvests.

This might be intentional behavior - technically we could reject overlaps from other in progress uploads. However I suspect that it will be way to complicated to deal with that scenario.

• [x] Scope overlap check to current harvest
• [x] Scope duplicate check to current harvest (appears to suffer from the same problem)

https://github.com/QutEcoacoustics/baw-server/blob/8914eb958b1f6bef3285a593e4954408d205cbbd/app/models/harvest_item.rb#L163-L170