Support for SNS Custom Resource Handling

[matthewjohnward]

I'd like to use this handler with an SNS triggered custom resource, to handle a multi account scenario rather than to lambda in the local account.

In theory the message content delivered to lambda could be handled in the same way but would have been through custom resource in CF > SNS Remote > Lambda? i.e rather than dealing with the event directly, something like json.loads(event['Records'][0]['Sns']['Message'])? It would be great to be able to use this handler in that scenario.