AWS: auto-publisher Lambda function

[pettazz]

Create the auto-publisher Lambda function which will take a draft bundle id, fetch and remove it from the s3 storage, unpack it, git pull the latest from the repo, apply the changes, commit, push to the repo (implicitly triggering the publish web hook)

To be triggered via CloudWatch scheduler.

Ensure notifications on failures, and bundle doesn't get deleted unless changes were successfully pushed to git