SLSCMN-10 middyfy Lambda events

[mwarman]

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• Follow italicized instructions to add detail to assist the reviewers.
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🔧 Change Summary

List the changes included in this pull request.

• Issue: SLSCMN-10
• Create a middleware utility function for Lambda event handlers (i.e. invocations by other Lambda functions)

📝 Checklist

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• Complete a self-review of changes
• Unit tests have been created or updated
• The code is free of [new] lint errors and warnings

🧪 Steps to Test

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1. No lint errors
2. Unit tests succeed

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