Fix message decoding

[cv65kr]

In situation when subscribe a queue to an SNS topic with RawMessageDelivery option set up and we push encoded JSON

{\"default\": \"{\\\"test\\\": \\\"xxxx\\\"}\"}

The message is forwarded and contains protocol:

{
    "Messages": [
        {
            "MessageId": "b6e8402a-2798-405c-9955-78c10061610a",
            "ReceiptHandle": "b6e8402a-2798-405c-9955-78c10061610a#cbcbd29e-f9a8-4321-b3b0-3f5631ff1a8b",
            "MD5OfBody": "7b2d325f1dac7c79cf89e1fcde3b2e1d",
            "Body": "{\"default\": \"{\\\"test\\\": \\\"xxxx\\\"}\"}",
            "Attributes": {
                "ApproximateFirstReceiveTimestamp": "1601971148229",
                "SenderId": "1601971148229",
                "ApproximateReceiveCount": "1",
                "SentTimestamp": "1601971148229"
            },
            "MD5OfMessageAttributes": "d41d8cd98f00b204e9800998ecf8427e"
        }
    ]
}

AWS in receive-message don't show the protocol of message but only message.

Expected result:

{
    "Messages": [
        {
            "MessageId": "b6e8402a-2798-405c-9955-78c10061610a",
            "ReceiptHandle": "b6e8402a-2798-405c-9955-78c10061610a#cbcbd29e-f9a8-4321-b3b0-3f5631ff1a8b",
            "MD5OfBody": "7b2d325f1dac7c79cf89e1fcde3b2e1d",
            "Body": "{\"test\": \"xxxx\"}",
            "Attributes": {
                "ApproximateFirstReceiveTimestamp": "1601971148229",
                "SenderId": "1601971148229",
                "ApproximateReceiveCount": "1",
                "SentTimestamp": "1601971148229"
            },
            "MD5OfMessageAttributes": "d41d8cd98f00b204e9800998ecf8427e"
        }
    ]
}