You can find a list of keyboard mappings if you Google for:
What are the keyboard controls for PS4
You'll find a reddit page.... if not try to search for:
ps4 keymap keyboard
It does not mention the PS button however, which would be needed to start the shutdown process, or to exit Netflix for that matter.

However, it's a very cheap solution to get a universal/programmable remote (like the popular logitech Harmony) to communicate with the PS4.
It fully suffices for browsing through the ps4 menu and starting and controlling a Netflix session, with pause, play, stop, fastforward, fastbackward.

If the PS4 Netflix application would have an exit option, you would be able to leave Netflix and scroll through the PS4 menu to the shutdown option to shut it down.

But unfortunately Netflix can only be exited by using the PS button. So that means you need to switch to your PS4 controller, or press the power button on you PS4 unit to shut it down.

I'm very happy with the additional functionality. If I want to stop watching Netflix, it's generally either because I'm going to play a game (so I need to switch to the PS4 controller anyway), or because I'm going to do something else, so I can switch of the PS4 by pressing the power button on the PS4 unit.

Perhaps if you have a full functional usb keyboard with many additional multimedia keys, you might be able to find a key combination that results in the PS-button behavior. Once you know what key combination you need, you could try to find a usb IR keyboard with these keys, and use the IR-sensor of that keyboard to connect to your PS4. Then use the keyboard to learn the trick to your universal remote.