telemetry message for factory end of line test

[Benhalor]

A new type of message should be added to send messages from the firmware to the UI during the factory end of line test
The following informations should be in this message :

• uint16_t stepNumber
• uint8_t stepStatus : 0 = fail, 1 = success, 2 = in progress
• String message : a string to display on the UI. No translation required because this is only a factory mode
• some numbers should be send, but due to the fact, that the amount and type of theses numbers is different at each message, it would be easier to send the numbers as text in the String message
• bool lastMessage : true if this is the last message

On the other direction, the UI should be able to send message to the firmware when the user clicks on the "NEXT" button

[dsferruzza]

1. I assume this new telemetry message would be send at a constant frequency and the current state changes, right?
2. Not sure about the success status value: receiving a message saying that step i is in progress should tell the UI that every step < i was a success, thus making the success status useless, right?
3. What will the UI do with the numbers? If this data is not structured now, it does not mean the firmware will be able to send whatever it wants, it just means that the UI will have to somehow parse it if it needs it (while I believe it should be the telemetry lib's job)
4. What is the point of the lastMessage field?

[dsferruzza]

This is not done yet, we need to define what data is sent in case of EOL success