rfc: move agent message index to dynamodb

[alanshaw]

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[volmedo]

This sounds like a great idea, DynamoDB is a good fit for storing index/map data.

For my own edification, which service writes/reads this index and what is its role in the system? (Maybe add this to the intro as a brief context description?)

[alanshaw]

For my own edification, which service writes/reads this index and what is its role in the system? (Maybe add this to the intro as a brief context description?)

@volmedo this is the upload service, so w3infra and w3up (soon to move to upload-service). These writes are performed by the agent message store, implemented here.