CCM-18398: Allow access to eventpub's event cache bucket to be restricted

[gareth-allan]

Description

This PR adds an event_cache_restrict_data_access boolean flag to the eventpub module's variables and uses it to set the enable_abac property and NHSE-RESTRICTED-PID tag on the module's event cache S3 bucket.

The updated module will be used (and has been tested) in this Digital Letters PR.

Context

This change is required because the Digital Letters domain contains PII (an NHS number) in some of its event payloads. This means that Digital Letters needs to be able to restrict access to the event cache S3 bucket in production accounts.

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

To ensure the utmost confidentiality and protect your and others privacy, we kindly ask you to NOT including PII (Personal Identifiable Information) / PID (Personal Identifiable Data) or any other sensitive data in this PR (Pull Request) and the codebase changes. We will remove any PR that do contain any sensitive information. We really appreciate your cooperation in this matter.

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