SqlSetup: Cannot install and apply GMSA accounts using the SqlSvcAccount and AgtSvcAccount variables

Problem description

The installation does not error out, it completes just fine except it doesn't apply our defined GMSAs to the instance and uses default local accounts.

Verbose logs

I don't see a problem in the logs

How to reproduce

run an installation and pass GMSAs for service account parameters: SqlSvcAccount and AgtSvcAccount

Expected behavior

The accounts given to parameters SqlSvcAccount and AgtSvcAccount would be the accounts running the SQL services

Current behavior

default local accounts are running services after the installation completes

Suggested solution

Add support for GMSAs

Operating system the target node is running

OsName               : Microsoft Windows Server 2019 Standard
OsOperatingSystemSKU : StandardServerEdition
OsArchitecture       : 64-bit
WindowsVersion       : 1809
WindowsBuildLabEx    : 17763.1.amd64fre.rs5_release.180914-1434
OsLanguage           : en-US
OsMuiLanguages       : {en-US}

PowerShell version and build the target node is running

Name                           Value
----                           -----
PSVersion                      5.1.17763.3770
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.17763.3770
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1

Module version used

SqlServerDsc 15.2.0  C:\Program Files\WindowsPowerShell\Modules\SqlServerDsc\15.2.0\SqlServerDsc.psd1

Start at the SqlSetup resource paths that process the SqlSvcAccount and AgtSvcAccount parameters, then reproduce the installation with GMSA values on the stated Windows and PowerShell versions. Trace how those parameters are applied to the SQL services. Done means the installation leaves both services running under the supplied GMSA accounts rather than default local accounts.