### 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_
"""
    The SQS publisher is responsible for publishing the SNS message to a subscribed SQS queue using `SQS.send_message`.
    For integrations and the format of message, see:
    https://docs.aws.amazon.com/sns/latest/dg/sns-sqs-as-subscriber.html
    """
    def _publish(self, context: SnsPublishContext, subscriber: SnsSubscription):
        message_context = context.message
        try:
            message_body = self.prepare_message(message_context, subscriber)
            kwargs = self.get_sqs_kwargs(msg_context=message_context, subscriber=subscriber)
        except Exception:
            LOG.exception("An internal error occurred while trying to format the message for SQS")
            return
        try:
            queue_url: str = sqs_queue_url_for_arn(subscriber["Endpoint"])
            region = extract_region_from_arn(subscriber["Endpoint"])
            sqs_client = connect_to(region_name=region).sqs.request_metadata(
                source_arn=subscriber["TopicArn"], service_principal="sns"
            )
            sqs_client.send_message(
                QueueUrl=queue_url,
                MessageBody=message_body,
                MessageSystemAttributes=create_sqs_system_attributes(context.request_headers),
                **kwargs,
            )