feat: Add account ID to GuardDuty event notification

[bruno]

Description

Always show the AWS AccountID that the GuardDuty event is related to.

I've modified the sample events and messages to add a bogus accountId. Running the pipenv commands as per the README made some formatting changes on mylambda.py, so I am leaving that as suggested by that run.

The snapshots also needed updating to reflect the fact that we now have an AccountID in the GuardDuty event/message.

It's my first contribution to this repo, so apologies in advance 😄

Motivation and Context

This PR was motivated by the same reasoning I saw in #164. We are using this module to send notifications from multiple AWS accounts to Slack and not having the AccountID visible in the notification was bugging us, as it makes the investigation slightly more tedious.

In order to add this attribute, I validated that even on a single (newly created) AWS account, the GuardDuty event always contains an AccountID attribute. The AWS documentation https://docs.aws.amazon.com/guardduty/latest/ug/guardduty_findings_cloudwatch.html seems to indicate this too. This was achieved by triggering the sample events from the AWS console.

Breaking Changes

How Has This Been Tested?

• I have updated at least one of the examples/* to demonstrate and validate my change(s)
• I have tested and validated these changes using one or more of the provided examples/* projects

• I have executed pre-commit run -a on my pull request

[bruno]

I am confused by the failing tests, as I ran the pre-commit run -a locally:

❯ TAG=latest
❯ docker run -e "USERID=$(id -u):$(id -g)" -v $(pwd):/lint -w /lint ghcr.io/antonbabenko/pre-commit-terraform:$TAG run -a
Unable to find image 'ghcr.io/antonbabenko/pre-commit-terraform:latest' locally
[...]
Digest: sha256:64ce1e4b99d85497fe646db0724669039b079b45fa8cd503b4dc23dbdca490ae
Status: Downloaded newer image for ghcr.io/antonbabenko/pre-commit-terraform:latest
[INFO] Initializing environment for https://github.com/antonbabenko/pre-commit-terraform.
[INFO] Initializing environment for https://github.com/pre-commit/pre-commit-hooks.
[INFO] Installing environment for https://github.com/pre-commit/pre-commit-hooks.
[INFO] Once installed this environment will be reused.
[INFO] This may take a few minutes...
Terraform fmt............................................................Passed
Terraform validate.......................................................Passed
Terraform docs...........................................................Passed
Terraform validate with tflint...........................................Passed
check for merge conflicts................................................Passed
fix end of files.........................................................Passed

Am I missing something?

[bryantbiggs]

it looks like this workflow didn't get updated yet. If you update the same file from here https://github.com/terraform-aws-modules/terraform-aws-eks/blob/master/.github/workflows/pre-commit.yml in this PR it should run the tests successfully

[bruno]

Sorry @bryantbiggs just noticed that GitHub was complaining about master having moved forward underneath me, so I have fixed that. Thank you for approving the PR 🙇

[antonbabenko]

This PR is included in version 5.6.0 🎉

[github-actions]

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