### 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_
return f"{external_url}/?Action=ConfirmSubscription&TopicArn={topic_arn}&Token={subscription_token}"
def create_unsubscribe_url(external_url, subscription_arn):
    return f"{external_url}/?Action=Unsubscribe&SubscriptionArn={subscription_arn}"
class SubscriptionFilter:
    def check_filter_policy_on_message_attributes(
        self, filter_policy: Dict, message_attributes: Dict
    ):
        for criteria, conditions in filter_policy.items():
            if not self._evaluate_filter_policy_conditions_on_attribute(
                conditions,
                message_attributes.get(criteria),
                field_exists=criteria in message_attributes,
            ):
                return False
        return True
    def check_filter_policy_on_message_body(self, filter_policy: dict, message_body: str):
        try:
            body = json.loads(message_body)
            if not isinstance(body, dict):
                return False
        except json.JSONDecodeError:
            
            
            return False
        return self._evaluate_nested_filter_policy_on_dict(filter_policy, payload=body)
    def _evaluate_nested_filter_policy_on_dict(self, filter_policy, payload: dict) -> bool: