fix: Handle case when NAP metadata directory doesn't exist

[edarzins]

When writing NAP metadata, create the metadata directory if it doesn't exist.

Proposed changes

• Create NAP metadata directory if it doesn't already exist
• Expanded unit test to cover this case

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• I have updated any relevant documentation (README.md)

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