Hello,
I am working with a SNS to SQS project, in it we want to use the feature `RawMessageBody` when subscribing.
By looking into the code I found that the attributes are not persisted, for example `RawMessageBody` is always set to 'false'. Elsewhere in the code the parameters seems to be correctly used and send transform the message accordingly.

I created a PR fixing this : https://github.com/localstack/localstack/pull/1234
Thank you 
test_data = [
        (
            'no filter with no attributes',
            {},
            {},
            True
        ),
        (
            'no filter with attributes',
            {},
            {'filter': {'Type': 'String', 'Value': 'type1'}},
            True
        ),
        (
            'exact string filter',