Allow deferred for private_key

[baurmatt]

This adds support for using the deferred function in Puppet 6:

include wireguard

wireguard::interface { 'wg0':
  private_key => Deferred('wireguard::genprivatekey', ['/etc/wireguard/wg0.key']),
  listen_port => 53098,
}

I would suggested reviewing/merging #20 first because it will extend the test matrix with Puppet 5/6 and will therefore ensure this change is tested on all supported Puppet versions.

Regarding tests for the Deferred usage: I think this isn't currently possible because I fail to see an option to pass the Deferred function in rspec through the params variable.

This differs from #6 because it adds a couple more things:

• Supports Puppet 4/5/6
• Allows the included function to be used as Deferred function
• Test for all changed/introduced function

[bastelfreak]

@baurmatt any chance you can rebase this?

[baurmatt]

@bastelfreak Done! :) Do you have merge rights? :)

[bastelfreak]

@baurmatt sadly I don't :( but I would like to use your code

@spacedog can you take a look please and merge this?

[bastelfreak]

@spacedog hey, any chance you can take a look?

[spacedog]

@baurmatt: could you please resolve conflicts as I made few changes to repository?