CCM-14062: routing e2e

[alexnuttall]

Description

Adds an e2e test for routing. Templates are seeded. AUTHORING letters are used.

Also adds template completion event assertons to routing-config.event.spec.ts. Using AUTHORING letters here means that letter completion events are currently missing (they are ignored by the publisher because they don't have the proofingEnabled flag).

Ported over the SQS/SNS-based EventSubscriber test util from core and replaced the existing s3 based util with it. Event cache buffering has been restored to the default since we don't need fast delivery for tests any more

Context

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
• If I have used the 'skip-trivy-package' label I have done so responsibly and in the knowledge that this is being fixed as part of a separate ticket/PR.

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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.

The base branch was changed.