[PLT-1227] Cost Anomaly alert to slack

[juliareynolds-nava]

🎫 Ticket

https://jira.cms.gov/browse/PLT-1227

🛠 Changes

Added a cost anomaly cost monitor and sns topic subscription. This is the first part of required work for this feature. A lambda to push alerts to slack will be completed in PLT-1361

ℹ️ Context

Users want to be alerted in Slack about significant cost fluctuations, so that we can take actions on addressing potential cost anomalies.

🧪 Validation

See check here: https://github.com/CMSgov/cdap/actions/runs/18880866713

[gsf]

Regarding the count argument errors you're seeing in the workflow runs, I think we need to iterate on the queue module.

As we discussed, add source and override documents to our sqs module as in the open source sqs module (but with simpler naming):

  source_policy_documents   = var.source_policy_documents
  override_policy_documents = var.override_policy_documents

If we add those variables to our module with [] as defaults then there should be nothing backwards-incompatible. That can be done in this PR.

Then pass a source document into the queue module, and define the sns topic subscription at the end of this file instead of passing in the topic arn.

This may still result in a need to run with -exclude arguments for the initial apply. Please ping me if that's the case.