Ensure CloudTrail logs are encrypted at rest using AWS KMS keys

[dsotirho-ucsc]

{
    "GeneratorIds": [
        "arn:aws:securityhub:::ruleset/cis-aws-foundations-benchmark/v/1.2.0/rule/2.7",
        "aws-foundational-security-best-practices/v/1.0.0/CloudTrail.2"
    ]
}

https://docs.aws.amazon.com/securityhub/latest/userguide/securityhub-cis-controls.html#securityhub-cis-controls-2.7
https://docs.aws.amazon.com/securityhub/latest/userguide/securityhub-standards-fsbp-controls.html#fsbp-cloudtrail-2

---

• Security design review completed; the Resolution of this issue does not …
  • … affect authentication; for example:
    • OAuth 2.0 with the application (API or Swagger UI)
    • Authentication of developers with Google Cloud APIs
    • Authentication of developers with AWS APIs
    • Authentication with a GitLab instance in the system
    • Password and 2FA authentication with GitHub
    • API access token authentication with GitHub
    • Authentication with
  • … affect the permissions of internal users like access to
    • Cloud resources on AWS and GCP
    • GitLab repositories, projects and groups, administration
    • an EC2 instance via SSH
    • GitHub issues, pull requests, commits, commit statuses, wikis, repositories, organizations
  • … affect the permissions of external users like access to
    • TDR snapshots
  • … affect permissions of service or bot accounts
    • Cloud resources on AWS and GCP
  • … affect audit logging in the system, like
    • adding, removing or changing a log message that represents an auditable event
    • changing the routing of log messages through the system
  • … affect monitoring of the system
  • … introduce a new software dependency like
    • Python packages on PYPI
    • Command-line utilities
    • Docker images
    • Terraform providers
  • … add an interface that exposes sensitive or confidential data at the security boundary
  • … affect the encryption of data at rest
  • … require persistence of sensitive or confidential data that might require encryption at rest
  • … require unencrypted transmission of data within the security boundary
  • … affect the network security layer; for example by
    • modifying, adding or removing firewall rules
    • modifying, adding or removing security groups
    • changing or adding a port a service, proxy or load balancer listens on
• Documentation on any unchecked boxes is provided in comments below

[hannes-ucsc]

Similar to #4715. We'll solve that one first.