The Infiltrate! quest card has two Forced actions, both are for the "beginning of your turn".
There don't appear to be rules governing the order that multiple actions must occur in when they happen at the same time and it's important in this case. So is it the owner's choice?
Is there an official FAQ yet?
Ok my interpretation would be:
*Both forced effects trigger
*Active player decides which order they will enter the FILO stack (First in Last out)
*Player will stack the 'Discard X card effect first'
*Player will stack the 'Add an extra token effect first'
*Stack will resolve with the player adding a token first and then forcing the opponent to discard the extra card.
Obviously there are windows between the effects for other players to play other effects that may cancel or affect the stack.
Admittedly this is all conjecture, but as much as I hate to say this...if this were Mtg, this is how it would play out (minus a few steps)