### 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_
self, sns_create_topic, sns_subscription, sns_create_platform_application, aws_client
    ):
        topic_arn = sns_create_topic()["TopicArn"]
        endpoints_arn = {}
        for platform_type in ["APNS", "GCM"]:
            application_platform_name = f"app-platform-{platform_type}-{short_uid()}"
            # C
            app_arn = sns_create_platform_application(
                Name=application_platform_name, Platform=platform_type, Attributes={}
            )["PlatformApplicationArn"]
            endpoint_arn = aws_client.sns.create_platform_endpoint(
                PlatformApplicationArn=app_arn, Token=short_uid()
            )["EndpointArn"]
            # s
            endpoints_arn[platform_type] = endpoint_arn
            # s
            sns_subscription(
                TopicArn=topic_arn,
                Protocol="application",
                Endpoint=endpoint_arn,
            )
        # n
        message = {