### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

I am running an SNS topic that publishes to a lambda function. The localstack code reads a type byte object from the lambda function invocation payload [here](https://github.com/localstack/localstack/blob/master/localstack/services/sns/publisher.py#L187) and then tries to dump the result into json [here](https://github.com/localstack/localstack/blob/master/localstack/services/sns/publisher.py#L863) which results in the following error:
```
sns_pub_0] l.services.sns.publisher   : Unable to run Lambda function on SNS message: Object of type bytes is not JSON serializable
```

### Expected Behavior

The payload bytes should be converted to a string before being dumped to json. The error should not be thrown.

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

docker-compose up
(Using the standard docker-compose.yaml)

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

```
awslocal sns publish --message file://sns/message.json --topic-arn arn:aws:sns:us-east-1:000000000000:<topic_name>
```

### Environment

```markdown
- OS: macOS Ventura 13.2.1
- LocalStack: latest
```


### Anything else?

_No response_
)
        snapshot.match("publish-msg-json", publish_response)
        msg = sqs_client.receive_message(
            QueueUrl=queue_url,
            AttributeNames=["All"],
            MessageAttributeNames=["All"],
            WaitTimeSeconds=3,
        )
        snapshot.match("json-delivery-msg-attrs", msg)
        # b
        # h
    @pytest.mark.only_localstack
    @pytest.mark.aws_validated
    @pytest.mark.parametrize("raw_message_delivery", [True, False])
    def test_subscribe_external_http_endpoint(
        self,
        sns_client,
        sns_create_http_endpoint,
        raw_message_delivery,
    ):
        # N
        topic_arn, subscription_arn, endpoint_url, server = sns_create_http_endpoint(
            raw_message_delivery
        )
        assert poll_condition(
            lambda: len(server.log) >= 1,
            timeout=5,
        )
        sub_request, _ = server.log[0]
        payload = sub_request.get_json(force=True)