[openvpn] Remove mandatory items

[okraits]

In certain situations, especially when modifying an existing openvpn config, it shouldn't be necessary to provide certain items as they might already exist in the openvpn config.

[coveralls]

Coverage remained the same at 99.635% when pulling 0968e43 on remove-mandatory-items into 599d40b on master.

[atb00ker]

Looks good, but deferring to Fed.

[okraits]

@nemesisdesign I rebased this to current master. Please let me know if there's anything which keeps this from getting merged.

[okraits]

@nemesisdesign What about this one? This is in the queue for one and a half year...

[nemesifier]

@nemesisdesign What about this one? This is in the queue for one and a half year...

Sorry for having forgotten this.
This can cause problems to existing systems which rely on this check, I was looking for an alternative way and I believe applying this change can be applied with monkey patching in your own system, I have done similar changes in a few deployments.

I want to bring up again the subject of #120 to add easy ways to enable changes to the backends, changes could mean enabling optional schema sections for openwrt packages that are not installed by default or register schema changes like this.

[okraits]

I'm already maintaining a patch for this for one and a half year and we use it since then without problems - that's why I wanted to get this upstream and get rid of the patch ;-)

[nemesifier]

@okraits instead of patching the library, you can apply this patch in your django project, import the module in the settings and update the schema dictionary there, you will not need to maintain a fork of netjsonconfig, that's how I have been doing it and it's working pretty well so I recommend it to you too.

[okraits]

@nemesisdesign Why did you close the PR? Don't you want to fix this issue?

[nemesifier]

@okraits as I said, this cannot be accepted as it can create issues on systems which rely on these checks. Instead of patching the library, you can apply this patch in your django project, import the module in the settings and update the schema dictionary there, you will not need to maintain a fork of netjsonconfig, that's how I have been doing it and it's working pretty well so I recommend it to you too. If I am missing something let me know and give me more details please.