Generate WSTEP cert/key

[rfairburn]

UPDATE: My understanding is that we can make it so the user doesn't have to plug anything into the UI/API nor env variables: Fleet generates and stores the WSTEP cert/key for the user.

(noahtalerman 2024-05-28)

Problem

I am happy to see that in https://github.com/fleetdm/fleet/issues/19014 we are adding the ability to manage APNS/SCEP for Apple MDM, but I would like to see the same level of support for Windows/WSTEP.

One of our goals was to simplify the process of supporting mdm via our terraform example. If a customer/prospect wishes to use windows MDM without this, no simplification is possible.

The existing render template would also not be Windows MDM friendly as well.

Potential solutions

1. Use the same method used in SCEP on https://github.com/fleetdm/fleet/issues/19014 for WSTEP