fix(iot): add mqtt version limitation (#5357)

* fix(iot): add mqtt version limitation

* Update pages/iot-hub/faq.mdx

* Apply suggestions from code review

Co-authored-by: Benedikt Rollik <[email protected]>

---------

Co-authored-by: Benedikt Rollik <[email protected]>

Author: RoRoJ

pages/iot-hub/concepts.mdx

@@ -66,6 +66,10 @@ Message filters restrict the messages a device can publish or subscribe to. Each
 
 Message Queuing Telemetry Transport (MQTT) is a lightweight publish/subscribe protocol for exchanging messages between devices and/or applications. Find out more about MQTT [on our blog](https://www.scaleway.com/en/blog/introduction-to-mqtt-protocol/).
 
+<Message type="note">
+  Scaleway IoT Hub supports MQTT v3.1, but not MQTT v5.
+</Message>
+
 ## Mutual TLS (mTLS)
 
 Mutual TLS is a method of mutual authentication. It indicates that both the TLS client and TLS server are required to authenticate each other. Each party must therefore possess a certificate to provide to the other, as well as a Certificate Authority to verify the certificate provided by the other party.

pages/iot-hub/faq.mdx

@@ -85,4 +85,8 @@ On a dedicated or High-Availability Hub, you are the only customer on the messag
 Any MQTT message between the Hub and a Device will be billed. If the message is bigger than 4 kB, then each 4 kB chunk of the message will be counted as a message for billing purposes. For example, a 9 kB message will be billed as 3 messages.
 
 ## What is the maximum message size?
-The maximum size for a message is 4 MB.
+The maximum size for a message is 4 MB.
+
+## Which versions of MQTT are supported by Scaleway IoT Hub?
+
+Scaleway IoT Hub supports MQTT v3.1, but not MQTT v5.