You should be able to tell by looking through the strip if it uses leds or bulbs?
I searched for a wiring instruction for this, but was surprised that I found nothing.
If it has leds, the two wires are 'polarised' which means one must be battery negative (ground) and the other wire will go to the stop light wire on the bike. Due to its small current, it should not affect CAN by putting up a warning, although it might just stop the warning if the rear bulb fails.
You have to find out/test which wire is to positive and which is negative. First I'd try an email to Givi. If you can get hold of a resistor of around 400 ohms, put that in series and connect the resistor and light unit across a 12 volt battery, then reverse the leads. If the unit glows very dim one way around that is the correct polarity so mark the wires. Remove the test resistor and connect the light unit straight to the battery. It should light at full brightness.
If the strip uses bulbs, then it doesn't matter which way around the wires are connected.