Add owners to app registration (AzureAD App)

[idangmic]

I would like to be able to add/update/remove owners of an app registration.
similarly to the method in Powershell.
https://docs.microsoft.com/en-us/powershell/module/azuread/add-azureadapplicationowner?view=azureadps-2.0

[yugangw-msft]

//CC: @mayurid
This is related with the on-going Graph Spec improvement so to support getting owner's service principals