Action to restart a service

[SteveL-MSFT]

Summary of the new feature / enhancement

As part of configuring a service, like sshd, the changes don't take effect until after the service is restarted. This can, today, be worked around by using the Microsoft.Windows/Service to stop and start it, but an action to restart would be better and also only restart if settings have changed since restarting a service can, for example, disconnect active clients.

Proposed technical implementation details (optional)

Ideally, it would work like:

$schema: https://aka.ms/dsc/schemas/v3/bundled/config/document.json
resources:
- name: Install PowerShell 7
  type: Microsoft.WinGet/Package
  properties:
    id: Microsoft.PowerShell
- name: Install SSHD
  type: Microsoft.Windows/FeatureOnDemandList
  properties:
    capabilities:
    - identity: OpenSSH.Server~~~~0.0.1.0
      state: Installed
- name: Add PS7 SSH Subsystem
  type: Microsoft.OpenSSH.SSHD/Subsystem
  properties:
    subsystem:
      name: powershell
      value: C:/progra~1/powershell/7/pwsh.exe -sshs
- name: Restart SSHD, if changed
  type: Microsoft.WIndows.Action/RestartService
  condition: "[stateChanged(resourceId('Microsoft.OpenSSH.SSHD/Subsystem','Add PS7 SSH Subsystem'))]"
  properties:
    name: sshd

This would need a new stateChanged() function that takes a resourceId() and returns true only if that resource resulted in a state change. Otherwise, the restart would be skipped.

[SteveL-MSFT]

stateChanged() function can just look at the output of the referenced resource and see if diffProperties is empty and return a bool