### 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_
fields["ResponseMetadata"]["HTTPStatusCode"] = response.status_code
            return parsed_xml_body
        snapshot.add_transformer(
            [
                snapshot.transform.key_value("RequestId"),
                snapshot.transform.key_value("Token"),
                snapshot.transform.regex(
                    r"(?i)(?<=URL[\"|']:\s[\"|'])(https?.*?)(?=/\?Action=ConfirmSubscription)",
                    replacement="<subscribe-domain>",
                ),
            ]
        )
        # 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)
        snapshot.match("subscription-confirmation", payload)
        assert payload["Type"] == "SubscriptionConfirmation"
        assert sub_request.headers["x-amz-sns-message-type"] == "SubscriptionConfirmation"
        assert "Signature" in payload
        assert "SigningCertURL" in payload
        token = payload["Token"]
        subscribe_url = payload["URL"]
        service_url, subscribe_url_path = payload["URL"].rsplit("/", maxsplit=1)