[FEATURE] OpenVPN Support

[pogmommy]

Is your feature request related to a problem? Please describe.
Right now nmrs only supports interfacing with wireguard VPN connections

Describe the solution you'd like
I'd like to see nmrs' current compatibility extended to OpenVPN connection types

For Developers- what would your solution be?

#92 outlined a plan which featured OpenVPN support, but appears to have been satisfied with the wireguard implementation. I'd imagine it may need to be adapted to changes in the codebase since. From my limited understanding, this would perhaps look something like:

• update VpnType and VpnCredentials models
• add OpenVPN to VpnType enum
• new OpenVPNPeer model
• new openvpn_builder module

Additional context
see #92

[cachebag]

@pogmommy Thank you! Indeed this was the original plan, but WireGuard proved to be easier to approach first. OpenVPN has always been in the pipeline though, I will get to it when I can but no promises at least for the next few months. Contributions are very welcome!