Ability to export PCKS#12 from certificates

[stottler]

Is your feature request related to existing pfSense functionality that is missing from the API? Please describe.
Yes this is an existing function in base pfSense

Is your feature request related to a problem? Please describe.
I would like the ability to export .p12 (PCKS#12) files from certificates tab.

Describe the solution you'd like
Ideally include this in the existing endpoint and just label the dict as 'p12'

Describe alternatives you've considered
Working on a solution atm since it's not implemented

Additional context
Since the client export feature of openvpn is a plugin and not native (and supposivly in the works for this api plugin) I need to make a work around which I've mostly done in python except for the .p12 file.