Fixes bugs in Print with AWS SDK v4

[njlr]

This PR fixes some bugs in AttributeValue.Print that were introduced by the upgrade to AWS SDK v4.
Also fixed is a bug where NS was printing as SN.
Test coverage is improved.

[bartelink]

these three are unused

[njlr]

Now removed 👍

[bartelink]

prefer <> null for these over isNotNull

But actually, I think these should use IsThingSet as a guard in order to correctly handle empty dictionaries when in uninitialized mode, which can still arise if people switch the default config mode to not leave lists/dictionaries null?

[njlr]

I switched over to the Is* properties 👍

[bartelink]

Thanks for catching these and especially for taking the time to add a test

As alluded to in the comments I suspect there may be some additional straggler = null, <> null, isNull, isNotNull checks that need to become .IsThingSet (many of which are my fault from the original PR, sorry)

[njlr]

Thanks for catching these and especially for taking the time to add a test

As alluded to in the comments I suspect there may be some additional straggler = null, <> null, isNull, isNotNull checks that need to become .IsThingSet (many of which are my fault from the original PR, sorry)

I will pick up the remainder in #88 and keep this PR focused on the utils / Print functions if that's OK?

[bartelink]

I will pick up the remainder in #88 and keep this PR focused on the utils / Print functions if that's OK?

That's fine with me; thanks for all the work (Sam will be doing merging/releasing and a final look-over; I just happen to be watching)

I had a quick scan and I'm not sure there are all that many other occurrences in the end, tho perhaps I didnt look hard enough. One thought was that perhaps the isNull and isNotNull helpers should go (I had thought they were the FSharp.Core ones)