BCDA-8208: Fix S3 path parsing

[kyeah]

🎫 Ticket

https://jira.cms.gov/browse/BCDA-8208

🛠 Changes

• Fix S3 path parsing

ℹ️ Context

I observed failures with the lambdas attempting to list files in S3 within the bfdeft01 prefix. This is not the correct prefix — the team-specific IAM roles can only access specific subfolders (i.e. bfdeft01/bcda, bfdeft01/dpc, etc.) so the lambdas should be trying to list files within those subfolders.

When parsing the S3 prefix from the SQS event, it needs to split from the last separator instead of the first separator.

🧪 Validation

Deployed to Dev and verified successful import by uploading a file (I basically did this part of the integration test manually:

bcda-app/.github/workflows/opt-out-import-test-integration.yml

Lines 47 to 48 in fabde15

	aws s3 cp --no-progress ../shared_files/synthetic1800MedicareFiles/test/T\#EFT.ON.ACO.NGD1800.DPRF.D181120.T1000009 \
	s3://bfd-test-eft/bfdeft01/bcda/in/T.NGD.DPC.RSP.D$(date +'%y%m%d').T$(date +'%H%M%S')1.IN

but fixed the filename since it's using the DPC filename)

Successful lambda logs

[austincanada]

LGTM