### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

Im using localstack via a local minikube cluster using the helm charts:

https://github.com/localstack/helm-charts

Ive set up the following topic and endpoint:

```bash
  awslocal sns create-topic --name test
  awslocal sns subscribe \
    --protocol http \
    --topic-arn arn:aws:sns:us-east-1:000000000000:test \
    --endpoint-url http://localstack:4566 \
    --notification-endpoint http://myapp:8000/subscribe
```

Ive got some code in a where I publish a message in the topic manually via boto3, and it calls my endpoint successfully  which I can also confirm from my logs of the pod running the endpoint:

` INFO:     10.244.0.40:40552 - "POST /subscribe HTTP/1.1" 200 OK`

However immediately after, I get an error from localstack pod that looks like:


```

 2023-04-01T01:15:55.238  INFO --- [   sns_pub_0] l.services.sns.publisher   : Received error on sending SNS message, putting to DLQ (if configured): object supporting the buffer API required
 2023-04-01T01:15:55.239 ERROR --- [   sns_pub_0] l.services.sns.publisher   : An internal error occurred while trying to send the SNS message SnsMessage(type='Notification', message={'default': {'foo': 'bar'}}, message_attributes={}, message_structure='json', subject='example subject', message_deduplication_id=None, message_group_id=None, token=None, message_id='6f150269-fe84-4daf-876f-9c7cfae99f87')
 Traceback (most recent call last):
   File "/opt/code/localstack/localstack/services/sns/publisher.py", line 444, in _publish
     store_delivery_log(message_context, subscriber, success=True, delivery=delivery)
   File "/opt/code/localstack/localstack/services/sns/publisher.py", line 853, in store_delivery_log
     "messageMD5Sum": md5(message),
   File "/opt/code/localstack/localstack/utils/strings.py", line 145, in md5
     m.update(to_bytes(string))
 TypeError: object supporting the buffer API required
 
 During handling of the above exception, another exception occurred:
 
 Traceback (most recent call last):
   File "/opt/code/localstack/localstack/services/sns/publisher.py", line 80, in publish
     self._publish(context=context, subscriber=subscriber)
   File "/opt/code/localstack/localstack/services/sns/publisher.py", line 451, in _publish
     store_delivery_log(message_context, subscriber, success=False)
   File "/opt/code/localstack/localstack/services/sns/publisher.py", line 853, in store_delivery_log
     "messageMD5Sum": md5(message),
   File "/opt/code/localstack/localstack/utils/strings.py", line 145, in md5
     m.update(to_bytes(string))
 TypeError: object supporting the buffer API required
```

From what I can tell, this doesnt appear to be a result of any code or data im in control or at least I dont believe it is but i could be wrong. As I mentioned, my subscription endpoint appears to work as expected and the exception is raised internally after from the local stack modules. Any direction on how I might be able to address this bug and prevent the exception would be great, thanks.


Thanks.

### Expected Behavior

Interanal exception doesnt occur after publish to topic.

### How are you starting LocalStack?

Custom (please describe below)

### Steps To Reproduce

As described in behavior.


### Environment

```markdown
- OS: Pop!_OS 22.04
- LocalStack: 1.4 
```


### Anything else?

As requested.
self,
        sns_create_topic,
        sqs_create_queue,
        sns_create_s,
        snapshot,
        content_based_deduplication,
        aws_client,
    ):
        topic_name = f"topic-{short_uid()}.fifo"
        queue_name = f"queue-{short_uid()}.fifo"
        topic_attributes = {"FifoTopic": "true"}
        queue_attributes = {"FifoQueue": "true"}
        if content_based_deduplication:
            topic_attributes["ContentBasedDeduplication"] = "true"
            queue_attributes["ContentBasedDeduplication"] = "true"
        topic_arn = sns_create_topic(
            Name=topic_name,