Add admin role usage alarm and tests

[richgreen-moj]

A reference to the issue / Description of it

ministryofjustice/modernisation-platform#7437

How does this PR fix the problem?

This adds a new alarm (and unit tests) which will trigger when anyone assumes the AdministratorAccess role in any MP accounts (Core/Member) in the MP low priority alerts channel.

How has this been tested?

I started by reviewing cloudtrail logs when accessing the role and finding the best way to pinpoint when the role is being assumed.
Then I created a new alarm and metric filter in the baselines module and manually applied it to the core-shared-services account (just because I needed an account that was already subscribed to the low priority slack alerts channel). I then assumed the admin role and observed that the alarm triggered and sent us a message.

See an example of the alert being raised:
https://moj-digital-tools.pagerduty.com/incidents/Q2NOMBHFB4MYRJ?utm_campaign=channel&utm_source=slack
https://mojdt.slack.com/archives/C02PFCG8M1R/p1724922501200269

[github-actions]

Trivy Scan Success

Show Output

```hcl

---

Trivy will check the following folders:
modules/securityhub-alarms test/securityhub-alarms-test

---

Running Trivy in modules/securityhub-alarms
2024-08-30T08:03:04Z INFO [db] Need to update DB
2024-08-30T08:03:04Z INFO [db] Downloading DB... repository="ghcr.io/aquasecurity/trivy-db:2"
2024-08-30T08:03:06Z INFO [vuln] Vulnerability scanning is enabled
2024-08-30T08:03:06Z INFO [misconfig] Misconfiguration scanning is enabled
2024-08-30T08:03:06Z INFO Need to update the built-in policies
2024-08-30T08:03:06Z INFO Downloading the built-in policies...
74.86 KiB / 74.86 KiB [-----------------------------------------------------------] 100.00% ? p/s 0s2024-08-30T08:03:06Z INFO [secret] Secret scanning is enabled
2024-08-30T08:03:06Z INFO [secret] If your scanning is slow, please try '--scanners vuln' to disable secret scanning
2024-08-30T08:03:06Z INFO [secret] Please see also https://aquasecurity.github.io/trivy/v0.54/docs/scanner/secret#recommendation for faster secret detection
2024-08-30T08:03:07Z INFO Number of language-specific files num=0
2024-08-30T08:03:07Z INFO Detected config files num=2
trivy_exitcode=0

---

Running Trivy in test/securityhub-alarms-test
2024-08-30T08:03:07Z INFO [vuln] Vulnerability scanning is enabled
2024-08-30T08:03:07Z INFO [misconfig] Misconfiguration scanning is enabled
2024-08-30T08:03:07Z INFO [secret] Secret scanning is enabled
2024-08-30T08:03:07Z INFO [secret] If your scanning is slow, please try '--scanners vuln' to disable secret scanning
2024-08-30T08:03:07Z INFO [secret] Please see also https://aquasecurity.github.io/trivy/v0.54/docs/scanner/secret#recommendation for faster secret detection
2024-08-30T08:03:08Z INFO Number of language-specific files num=0
2024-08-30T08:03:08Z INFO Detected config files num=2
trivy_exitcode=0

</details> #### `Checkov Scan` Success
<details><summary>Show Output</summary>

```hcl

*****************************

Checkov will check the following folders:
modules/securityhub-alarms test/securityhub-alarms-test

*****************************

Running Checkov in modules/securityhub-alarms
Excluding the following checks: CKV_GIT_1,CKV_AWS_126,CKV2_AWS_38,CKV2_AWS_39
terraform scan results:

Passed checks: 36, Failed checks: 0, Skipped checks: 3


checkov_exitcode=0

*****************************

Running Checkov in test/securityhub-alarms-test
Excluding the following checks: CKV_GIT_1,CKV_AWS_126,CKV2_AWS_38,CKV2_AWS_39
terraform scan results:

Passed checks: 38, Failed checks: 0, Skipped checks: 3


checkov_exitcode=0

CTFLint Scan Success

Show Output

*****************************

Setting default tflint config...
Running tflint --init...
Installing "terraform" plugin...
Installed "terraform" (source: github.com/terraform-linters/tflint-ruleset-terraform, version: 0.5.0)
tflint will check the following folders:
modules/securityhub-alarms test/securityhub-alarms-test

*****************************

Running tflint in modules/securityhub-alarms
Excluding the following checks: terraform_unused_declarations
tflint_exitcode=0

*****************************

Running tflint in test/securityhub-alarms-test
Excluding the following checks: terraform_unused_declarations
tflint_exitcode=0

Trivy Scan Success

Show Output

*****************************

Trivy will check the following folders:
modules/securityhub-alarms test/securityhub-alarms-test

*****************************

Running Trivy in modules/securityhub-alarms
2024-08-30T08:03:04Z	INFO	[db] Need to update DB
2024-08-30T08:03:04Z	INFO	[db] Downloading DB...	repository="ghcr.io/aquasecurity/trivy-db:2"
2024-08-30T08:03:06Z	INFO	[vuln] Vulnerability scanning is enabled
2024-08-30T08:03:06Z	INFO	[misconfig] Misconfiguration scanning is enabled
2024-08-30T08:03:06Z	INFO	Need to update the built-in policies
2024-08-30T08:03:06Z	INFO	Downloading the built-in policies...
74.86 KiB / 74.86 KiB [-----------------------------------------------------------] 100.00% ? p/s 0s2024-08-30T08:03:06Z	INFO	[secret] Secret scanning is enabled
2024-08-30T08:03:06Z	INFO	[secret] If your scanning is slow, please try '--scanners vuln' to disable secret scanning
2024-08-30T08:03:06Z	INFO	[secret] Please see also https://aquasecurity.github.io/trivy/v0.54/docs/scanner/secret#recommendation for faster secret detection
2024-08-30T08:03:07Z	INFO	Number of language-specific files	num=0
2024-08-30T08:03:07Z	INFO	Detected config files	num=2
trivy_exitcode=0

*****************************

Running Trivy in test/securityhub-alarms-test
2024-08-30T08:03:07Z	INFO	[vuln] Vulnerability scanning is enabled
2024-08-30T08:03:07Z	INFO	[misconfig] Misconfiguration scanning is enabled
2024-08-30T08:03:07Z	INFO	[secret] Secret scanning is enabled
2024-08-30T08:03:07Z	INFO	[secret] If your scanning is slow, please try '--scanners vuln' to disable secret scanning
2024-08-30T08:03:07Z	INFO	[secret] Please see also https://aquasecurity.github.io/trivy/v0.54/docs/scanner/secret#recommendation for faster secret detection
2024-08-30T08:03:08Z	INFO	Number of language-specific files	num=0
2024-08-30T08:03:08Z	INFO	Detected config files	num=2
trivy_exitcode=0

[ewastempel]

nice one