FOdurationSource - missing a NotApllicable code

[KirstenBirchHaakansson]

FOduration is only mandatory when FTsampler == “Observer” and FTsamplingType == “at-sea”, but FOdurationSource is always mandatory. This is a bit inconsistent, so

Either FOdurationSource needs a NotApplicable code (//vocab.ices.dk/?ref=1679)
or FOdurationSource should only be mandatory when FTsampler == “Observer” and FTsamplingType == “at-sea”

[HenrikK-N]

The Core Group agree that the code 'NotApplicable' should be added to the code type 'DurationSource' to solve the issue for the field FOdurationSource.

[HenrikK-N]

The code 'NotApplicable' have been requested added to the code type 'DurationSource'.