Expand on the CloudTrail event

[martinjlowm]

📬 Issue #, if available: N/A

✍️ Description of changes: The initial contribution of the CloudTrail event was not complete, but rather constructed from a handful of event examples. The structure is documented at:

• https://docs.aws.amazon.com/awscloudtrail/latest/userguide/cloudtrail-event-reference-user-identity.html

which indicates a number of optional fields and more fields that weren't already covered.

🔏 By submitting this pull request

• [x] I confirm that I've ran cargo +nightly fmt.
• [x] I confirm that I've ran cargo clippy --fix.
• [x] I confirm that I've made a best effort attempt to update all relevant documentation.
• [x] I confirm that my contribution is made under the terms of the Apache 2.0 license.