OfficeOnlineServerFarm: InternalURL should not be mandatory

[shurick81]

Details of the scenario you tried and the problem that is occurring

I am trying to build a farm, similar to what MS describes in the very first example: https://docs.microsoft.com/en-us/powershell/module/officewebapps/new-officewebappsfarm?view=officewebapps-ps

In this example, InternalURL is not specified, because only ExternalURL is in use.

Verbose logs showing the problem

Suggested solution to the issue

Change parameters validation

The DSC configuration that is used to reproduce the issue (as detailed as possible)

            OfficeOnlineServerFarm Farm
            {
                ExternalURL                 = "https://$($mainParameters.OOSHostName)"
                EditingEnabled              = $true
                CertificateName             = $mainParameters.OOSHostName
                LogLocation                 = $logFolder
                CacheLocation               = "$workingFolder\d"
            }

The operating system the target node is running

Win 2019

Version and build of PowerShell the target node is running

5.1

Version of the DSC module that was used ('dev' if using current dev branch)

1.2

[ykuijs]

The InternalURL property is specified as the Key property and therefore is always mandatory. To allow the above scenario, we need a new property.

Isn't the IsSingleInstance property better here: https://docs.microsoft.com/en-us/powershell/dsc/resources/singleinstance

A farm should only be created once on a server, so there should only be one instance of this property per server. The same is true for OfficeOnlineServerMachine.