The ingest Lambda is never invoked when objects land in the bucket.
Bucket notification: s3:ObjectCreated:* -> Lambda function "ingest", no
prefix/suffix filter. Uploads (PutObject) succeed and the objects appear in the
bucket, but the Lambda's CloudWatch Logs show zero invocations and there is no
error returned to the uploader.

Source bucket ARN: arn:aws:s3:::ingest-source
Lambda function ARN: arn:aws:lambda:us-east-1:111122223333:function:ingest

Attached: lambda-get-policy.json (output of `aws lambda get-policy`).
