CCM-15633: Subscribe Digital Letters to paperletteroptedout channel statuses

[gareth-allan]

Description

This PR adds a new rule and target to send uk.nhs.notify.channel.status.PUBLISHED.v1 events with a data.supplierStatus value of paperletteroptedout to the Digital Letters event bus.

The schema for uk.nhs.notify.channel.status.PUBLISHED.v1 events is available here.

Context

To determine whether a digital letter has been read by a patient within the NHS App, a new callback status of paperletteroptedout will be produced by the NHS app and then published by core to the shared event bus. Digital Letters needs to subscribe to these events to know what the read status of the PDF letter is, so that we can decide whether to cascade to a paper letter or not, ensuring that comms still reach patients as trusts expect them to.

Type of changes

• Refactoring (non-breaking change)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would change existing functionality)
• Bug fix (non-breaking change which fixes an issue)

Checklist

• I am familiar with the contributing guidelines
• I have followed the code style of the project
• I have added tests to cover my changes
• I have updated the documentation accordingly
• This PR is a result of pair or mob programming

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Sensitive Information Declaration

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• I confirm that neither PII/PID nor sensitive data are included in this PR and the codebase changes.