### Is there an existing issue for this?

- [X] I have searched the existing issues

### Feature description

SNS allows for the publishing of messages to an SMS destination with a phone number. Those messages are logged and stored in the `SnsStore`, but there is no way to retrieve them for verification. The request here is to expose a new endpoint which returns SMS messages from the store, similar to the one made available to retrieve email messages sent via SES.

### 🧑‍💻 Implementation

The `SNSServicePlatformEndpointMessagesApiResource` class makes endpoints available for accessing platform endpoint messages sent via SNS. A similar resource class could be implemented to provide new endpoints for accessing SMS messages.

Given that interaction platform endpoint messages is exposed at the path `/_aws/sns/platform-endpoint-messages`, SMS message interaction would presumably be exposed at `/_aws/sns/sms-messages`. A `GET` endpoint could accept an optional `phoneNumber` query parameter to filter messages based on the destination phone number.

```python
class SNSServiceSMSMessagesApiResource:
  @route(sns_constants.SMS_MSGS_ENDPOINT, methods=["GET"])
    def on_get(self, request: Request):
      account_id = #...
      region = #...
      filter_phone_number = request.args.get("phoneNumber")
      # get store; conditionally filter messages based on filter_phone_number
```

### Anything else?

_No response_
queue_arn = sqs_queue_arn(queue_url=queue_url)
        with pytest.raises(ClientError) as e:
            aws_client.sns.set_subscription_attributes(
                SubscriptionArn=subscription["SubscriptionArn"],
                AttributeName="RedrivePolicy",
                AttributeValue=json.dumps({"deadLetterTargetArn": queue_arn}),
            )
        snapshot.match("regular-queue-for-dlq-of-fifo-topic", e.value.response)
        with pytest.raises(ClientError) as e:
            aws_client.sns.publish(TopicArn=fifo_topic_arn, Message="test")
        assert e.match("MessageGroupId")
        snapshot.match("no-msg-group-id", e.value.response)
        with pytest.raises(ClientError) as e:
            aws_client.sns.publish(
                TopicArn=fifo_topic_arn, Message="test", MessageGroupId=short_uid()
            )
        # i
        assert e.match("MessageDeduplicationId")
        assert e.match("ContentBasedDeduplication")
        snapshot.match("no-dedup-policy", e.value.response)
        with pytest.raises(ClientError) as e:
            aws_client.sns.publish(
                TopicArn=topic_arn, Message="test", MessageDeduplicationId=short_uid()
            )
        assert e.match("MessageDeduplicationId")
        snapshot.match("no-msg-dedup-regular-topic", e.value.response)
        with pytest.raises(ClientError) as e:
            aws_client.sns.publish(TopicArn=topic_arn, Message="test", MessageGroupId=short_uid())
        assert e.match("MessageGroupId")
        snapshot.match("no-msg-group-id-regular-topic", e.value.response)