### 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, ctx: SnsPublishContext, topic_arn: str, subscription_arn: str
    ) -> None:
        """
        This allows us to publish specific HTTP(S) messages specific to those endpoints, namely
        `SubscriptionConfirmation` and `UnsubscribeConfirmation`. Those are "topic" messages in shape, but are sent
        only to the endpoint subscribing or unsubscribing.
        This is only used internally.
        Note: might be needed for multi account SQS and Lambda `SubscriptionConfirmation`
        :param ctx: SnsPublishContext
        :param topic_arn: the topic of the subscriber
        :param subscription_arn: the ARN of the subscriber
        :return: None
        """
        subscriber = ctx.store.subscriptions.get(subscription_arn)
        if not subscriber:
            return
        notifier = self.topic_notifiers[subscriber["Protocol"]]
        LOG.debug(
            "Topic '%s' publishing '%s' to subscribed '%s' with protocol '%s' (Id='%s', Subscription='%s')",
            topic_arn,
            ctx.message.type,
            subscription_arn,
            subscriber["Protocol"],
            ctx.message.message_id,
            subscriber.get("Endpoint"),
        )
        self.executor.submit(notifier.publish, context=ctx, subscriber=subscriber)