### 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,
        context: RequestContext,
        topic_arn: topicARN,
        token: String,
        authenticate_on_unsubscribe: authenticateOnUnsubscribe = None,
    ) -> ConfirmSubscriptionResponse:
        
        
        
        
        try:
            parsed_arn = parse_arn(topic_arn)
        except InvalidArnException:
            raise InvalidParameterException("Invalid parameter: Topic")
        store = self.get_store(account_id=parsed_arn["account"], region_name=parsed_arn["region"])
        
        if parsed_arn["region"] != get_region_from_subscription_token(token):
            raise InvalidParameterException("Invalid parameter: Topic")
        subscription_arn = store.subscription_tokens.get(token)
        if not subscription_arn:
            raise InvalidParameterException("Invalid parameter: Token")
        subscription = store.subscriptions.get(subscription_arn)
        if not subscription:
            
            raise InvalidParameterException("Invalid parameter: Token")
        
        if subscription.get("PendingConfirmation") == "false":