add extra_configs

[oliverkurth]

Add extra_configs configuration to ova-compose. This creates ExtraConfig items to the VirtualHardwareSection section.

The config is a dictionary with the key as key and each item is a dictionary with the keys value containing the value and the optional key required which is a boolean. Example:

extra_configs:
    feature.enabled:
        required: false
        value: true
    log.rotateSize:
        value: 2048000

The value can be a string, boolean or any type that can be converted to a string with python's str(). If required is unset it will be unset in the OVF as well. So the default of the backend will take effect (which is "true").

Example output:

      <vmw:ExtraConfig vmw:key="feature.enabled" vmw:value="true" vmw:required="false"/>
      <vmw:ExtraConfig vmw:key="log.rotateSize" vmw:value="2048000"/>
...
    </ovf:VirtualHardwareSection>