CCM-16644: Add an eventsub Module

[gareth-allan]

Description

Add the eventsub module from nhs-notify-supplier-api so that it can also be used in the reporting domain.

Context

The reporting domain needs to use the same pattern for subscribing to events from the shared event bus as the Supplier API already uses, and given that the supplier API already includes a Terraform module to implement this pattern, it makes sense to extract that module here to allow for reuse.

Validation

I used the new eventsub module in this PR in the nhs-notify-reporting repository: NHSDigital/nhs-notify-reporting#242

I then deployed this branch of nhs-notify-reporting: https://github.com/NHSDigital/nhs-notify-internal/actions/runs/25057676077

Deployed Resources

SNS Topic:

Firehose Stream:

S3 Bucket:

Glue Crawler:

Sending a Test Message

I then published a test message to the SNS topic:

Eventually, a file appeared in the S3 bucket:

The content of the file was as follows (formatted for readability):

{
  "Type": "Notification",
  "MessageId": "00cfc587-9975-5cf8-be5c-a7ed45c5edc7",
  "TopicArn": "arn:aws:sns:eu-west-2:381492132479:nhs-notify-main-reporting-eventsub",
  "Subject": "test",
  "Message": "{\n  \"test\": \"This is a test\"\n}",
  "Timestamp": "2026-04-28T16:04:00.169Z",
  "UnsubscribeURL": "https://sns.eu-west-2.amazonaws.com/?Action=Unsubscribe&SubscriptionArn=arn:aws:sns:eu-west-2:381492132479:nhs-notify-main-reporting-eventsub:82b03e51-7e7b-4d17-8ee8-8ab025ba56c8"
}

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

[gareth-allan]

It's been agreed that the reporting domain does not need to use the eventsub module, so I'm closing this PR. I don't think there's value in extracting the module from the supplier-api unless we know it's needed elsewhere.