Security and Encryption for Storage service

[sarahxxu]

Encryption at rest is enabled by default.

https://docs.microsoft.com/en-us/azure/security/fundamentals/encryption-models
Both Blob and Cosmos have options for server-side managed keys. Blob has an option for client-side client-managed key

This storage should ideally not be seen as secret vault or PII data that requires further compliance

[meryllblanchet]

This could fit in the security guide here: https://github.com/AdobeDocs/project-firefly/blob/master/guides/security_overview.md#files--state-services