LGA-4177: add new secret to secret-manager for cla_backend

[joselopez-moj]

We have added a new endpoint to read diversity data, the data needs the passphrase to get decrypted.

[Sablu M (sablumiah)]

Terraform Plan Summary

Terraform Plan: 3 to be created, 0 to be destroyed, 3 to be updated, 0 to be replaced and 74 unchanged.

Resources to create:

+ module.secret.aws_secretsmanager_secret.secret["diversity-mcc-passphrase"]
+ module.secret.kubernetes_manifest.external_secrets["diversity-mcc-passphrase"]
+ module.secret.random_id.secret_name["diversity-mcc-passphrase"]

Resources to update:

! module.cla_backend_metabase_rds.aws_db_parameter_group.custom_parameters
! module.opensearch_alert.opensearch_monitor.opensearch_alert
! pingdom_check.laa-cla-backend-pingdom

[Sablu M (sablumiah)]

This PR CANNOT be auto approved and requires manual approval from the Cloud Platform team.
Reason:
🕵️‍♂️ Manual review required: OPA auto approve policy checks did not pass.

Test	Passed?	Reason
allowlist	❌	This PR includes changes to modules / resources which are not on the allowlist, so we can't auto approve these changes. Please request a Cloud Platform team member's review in #ask-cloud-platform
ecr	✅	Valid ECR related terraform changes
hmpps-template	✅	Valid hmpps template related terraform changes
irsa	✅	Valid irsa related terraform changes
kubernetes_secret	✅	Valid K8s secret related terraform changes
rds	✅	Valid RDS module related terraform changes
secrets_manager	✅	Valid secrets manager related terraform changes
service_pod	✅	Valid Service pod related changes
sns	✅	Valid sns related terraform changes

Please raise it in #ask-cloud-platform Slack channel.