### 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,
        platform_application_arn: String,
        token: String,
        custom_user_data: String = None,
        attributes: MapStringToString = None,
    ) -> CreateEndpointResponse:
        
        
        try:
            result: CreateEndpointResponse = call_moto(context)
        except CommonServiceException as e:
            
            if "DuplicateEndpoint" in e.code:
                moto_sns_backend = self.get_moto_backend(context.account_id, context.region)
                for e in moto_sns_backend.platform_endpoints.values():
                    if e.token == token:
                        if custom_user_data and custom_user_data != e.custom_user_data:
                            
                            raise CommonServiceException(
                                code="DuplicateEndpoint",
                                message=f"Endpoint already exist for token: {token} with different attributes",
                            )
            raise
        return result
    def unsubscribe(self, context: RequestContext, subscription_arn: subscriptionARN) -> None: