NIAD-1201: Add support for NHS002 message types

[andrewwa-kainos]

Description

Currently they are expected to be the same as NHS003. Future stories will amend the allowed fields and update the integration tests so they start to look like real NHS002 messages.

Jira Ticket

https://gpitbjss.atlassian.net/browse/NIAD-1201

Checklist

These are items (excluding GitHub Checks) which should be confirmed before a branch is ready to merge.

• [x] Acceptance Criteria met
• [x] Commit messages are meaningful
• [ ] Manually tested
• [x] Self-reviewed your code
• [ ] Code reviewed from two other developers
• [x] If your pull request depends on any other, please link them in the description
• [x] main branch is passing/green on CI
• [x] Add/update any relevant documentation