Refactor: Move AWS and DB clients to new app/clients folder

[katybaulch]

Description

Move session.py under clients/db as part of backend refactor.

Proposed version

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Type of change

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• Bug fix
• New feature
• Breaking change
• GitHub workflow update
• Documentation update
• Refactor legacy code
• Dependency update

How Has This Been Tested?

Please describe the tests that you added to verify your changes.

Reviewer Checklist

• DB_CLIENT DEPENDENCY IS ON THE LATEST VERSION
• The PR represents a single feature (small driveby fixes are also ok)
• The PR includes tests that are sufficient for the level of risk
• The code is sufficiently commented, particularly in hard-to-understand areas
• Any required documentation updates have been made
• Any TODOs added are captured in future tickets
• No FIXMEs remain

[annaCPR]

all good!