implement aws secrets manager

instead of keeping bot token and api keys stored locally on the box, configure a lambda job to read secrets stored in the AWS Secrets manager. the bot should call the lambda job, which should deliver a JSON object of the key (we should decrypt the key within the application - not from the manager).

[AWS Secrets Manager](https://aws.amazon.com/secrets-manager/getting-started/)
[AWS Lambda - Python 3.6](https://docs.aws.amazon.com/lambda/latest/dg/python-programming-model.html)

Start with the linked AWS Secrets Manager getting-started guide and the AWS Lambda Python 3.6 programming-model guide; the issue names no repository files, entry points, or tests. Done means the bot no longer reads tokens and API keys from local storage, obtains them through the Lambda-returned JSON object, and decrypts them within the application.

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