NIAD-3134 - Add confidentialityCode support for DocumentReference

[martin-nhs]

What

This pull request introduces an enhancement to the DocumentReferenceMapper.java class, enabling it to detect the presence of a confidentialityCode with the value NOPAT at the RCMRMT030101UKExternalDocument level. If this code is identified, the system will automatically append meta.security with the corresponding NOPAT value to the resource. If the code is absent, no modifications will be made.

Why

Please see the ticket for more information.

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• I have performed a self-review of my code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have updated the Changelog with details of my change in the UNRELEASED section if this change will affect end users
• A corresponding change has been made to the Mapping Documentation repository

Please refer to this PR for the mapping documentation changes.