[Enhancement] Custom OpenVPN configuration

[mazhead]

Is your feature request related to a problem? Please describe. A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

I was unable to add custom options to OpenVPN configuration. There are many options which could benefit the user. In a particular example adding a pidfile can give the possibility to restart systemd service and monitor if we use the VPN.

This opens a possibility to stop services which depend on the VPN to prevent IP leaking. E.g. killswitch but on application level.

This is not the only use case as there are many more options which could be added.

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I have created the changes in my fork: https://github.com/mazhead/linux-cli/commit/d209523b23d1ddb75563c77826611a8ce28d6311

But as the contribution guide states, I should create a issue before creating a pull requests.

Describe alternatives you've considered A clear and concise description of any alternative solutions or features you've considered.

There is currently no other way (known to me) how to add any options to the openvpn config file as the jinja gets templated out before every config.

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