panos_zone mode external provide external vsys parameter

[kingfetty]

Is your feature request related to a problem?

The current panos_zone module does not have a parameter to specify the external zone when using mode 'external' to provision zones.

Describe the solution you'd like

provide a parameter to specify the external zone to associate for the next hop and implement the underlying logic to materialize this setting.

Describe alternatives you've considered

writing generic xml api payload to provide the external zones vsys next-hop

Additional context

External zones are zones that link from from a source vsys to a destination vsys. The module supports specifying the mode of the zone to be 'external' but that is an incomplete zone until a specified destination vsys is specified.

[kingfetty]

A layer3 zone provides the xml element
<network><layer3><member>INTERFACE_NAME</member></layer3></network>

An external zone provides the xml element

<network><external><member>VSYS_NAME</member></external></network>