only use vApp properties that are UserConfigurable

[adarobin]

This PR resolves #394 by ignoring vApp attributes that have UserConfigurable set to False.

[bill-rich]

Thanks @adarobin. This looks really great. Would it be possible to get an error thrown when a configuration attempts to set a non user configurable property? That way there won't be any confusion on why properties are being ignored.

[adarobin]

@bill-rich Not opposed to adding a message, but I'm not sure how to handle that. If you look at #394, properties that are not user configurable are getting pulled in regardless of if they are actually in the Terraform code or not.

For example, if I attempt to deploy a Nested ESXi OVA without this patch the deployment will fail as the vApp contains the property guestinfo.debug with userConfigurable set to false. This happens with or without guestinfo.debug being declared in Terraform code. This is because Terraform is copying all of the existing vApp properties from the source VM into the ConfigSpec without regard to if they are userConfigurable or not.

I worked around this by ignoring all properties with userConfigurable set to false.

[adarobin]

@bill-rich My brain isn't fully working on a Monday. It looks like the existing error handling that is right after this change is already taking care of this. If I try setting guestinfo.debug in my code I get thrown this error:

1 error(s) occurred:

* module.adarobin-dev-cluster.vsphere_virtual_machine.esxi: 1 error(s) occurred:

* vsphere_virtual_machine.esxi: error reconfiguring virtual machine: error in virtual machine configuration: unsupported vApp properties in vapp.properties: [guestinfo.debug]

Terraform does not automatically rollback in the face of errors.
Instead, your Terraform state file has been partially updated with
any resources that successfully completed. Please address the error
above and apply again to incrementally change your infrastructure.

[adarobin]

Just pushed code that should do what you are asking. This is what I see if I specify guestinfo.debug in my code now:

1 error(s) occurred:

* module.adarobin-dev-cluster.vsphere_virtual_machine.esxi: 1 error(s) occurred:

* vsphere_virtual_machine.esxi: error reconfiguring virtual machine: error in virtual machine configuration: vApp property with userConfigurable=false specified in vapp.properties: [guestinfo.debug]

Terraform does not automatically rollback in the face of errors.
Instead, your Terraform state file has been partially updated with
any resources that successfully completed. Please address the error
above and apply again to incrementally change your infrastructure.```

[adarobin]

@bill-rich thoughts on the latest code?

[bill-rich]

Thanks for adding in the error message. This looks ready to merge!