Add support for `actions`

[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

[ThomasNieto]

It would be nice if the restart service action hooked into the restartRequired canonical property. If that hook is added when the config doc is completed the DSC should not indicate that the service is needed to be restarted. This would be to prevent the config doc and higher order tool from cycling the service twice.

[SteveL-MSFT]

WG discussed this and current proposal for using an action in config:

$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
  notifications:
    - actionType: Microsoft.Windows.Service/Restart
      parameters:
        serviceName: sshd
      trigger: stateChanged
  properties:
    subsystem:
      name: powershell
      value: C:/progra~1/powershell/7/pwsh.exe -sshs

New action specific manifest:

$schema: https://aka.ms/dsc/schemas/v3/bundled/action/manifest.json
type: Microsoft.Windows.Service/Restart
version: 0.1.0
description: Restarts a Windows service.
invoke:
  executable: restart_service
  args:
    - jsonInputArg: '--input'
schema:
   ...
exitCodes:
  - 0: Service restarted successfully.
  - 1: Service not found.
  - 2: Failed to restart the service.

[SteveL-MSFT]

Actions will require condition to be not empty