### 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_
try:
        return parse_arn(topic_arn)
    except InvalidArnException:
        count = len(topic_arn.split(":"))
        raise InvalidParameterException(
            f"Invalid parameter: TopicArn Reason: An ARN must have at least 6 elements, not {count}"
        )
def encode_subscription_token_with_region(region: str) -> str:
    """
    Create a 64 characters Subscription Token with the region encoded
    :param region:
    :return: a subscription token with the region encoded
    """
    return ((region.encode() + b"/").hex() + short_uid() * 8)[:64]
def get_region_from_subscription_token(token: str) -> str:
    """
    Try to decode and return the region from a subscription token
    :param token:
    :return: the region if able to decode it
    :raises: InvalidParameterException if the token is invalid
    """
    try:
        region = token.split("2f", maxsplit=1)[0]
        return bytes.fromhex(region).decode("utf-8")
    except (IndexError, ValueError, TypeError, UnicodeDecodeError):
        raise InvalidParameterException("Invalid parameter: Token")
def register_sns_api_resource(router: Router):