Harvests > API > Should plant part be the 'first'

[CloCkWeRX]

https://github.com/Growstuff/growstuff/pull/4237/files#diff-5a5f1924ecfd79e47c20bdbb1ba3a5403b41aef958f5bf490bd8c64bb91d408cR10

Not ideal, a default of 'whole plant' would be a bit better. But we don't have a plant part API endpoint at the moment, so it's a mess.