OpenVPN Client Specific Overwrites - allow custom iroute input

[AdSchellevis]

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Is your feature request related to a problem? Please describe.

In an attempt to drop free text input, we should add options that are required in common scenario's. One of these are the iroute statements in client specific overwrites so one can teach openvpn to which client traffic should be forwarded.

Describe the solution you like

Most practical is likely just to add a comma separated text field for networks in cidr format which should translate into statements like iroute 192.168.4.0 255.255.255.0 Another option could be to add a checkbox "generate iroute's for provided remote networks" in overwrites for the remote networks defined..

Describe alternatives you considered

none

Additional context

https://openvpn.net/community-resources/expanding-the-scope-of-the-vpn-to-include-additional-machines-on-either-the-client-or-server-subnet/

https://openvpn.net/community-resources/reference-manual-for-openvpn-2-4/