isSaving parameter on @Shared to track if a save is in progress

[woodymelling]

I was working on implementing a SharedKey thats just based on making graphql queries and mutation for a specific type. The implementaton is pretty trivial, and just makes a query in the load block, and makes a mutation in the save block, with the subscription being empty (for now). This is basically the apps source of truth for the users settings, and we can let the user update it, synchronizing wit the server

The SharedKey conformance is straightforward, and lets us do this which works as expected.

struct AccountSettings {
  var settingOne = false
  var settingTwo = false
  var settingthree = false
}

struct SettingsView: View {
  @Shared(.accountSettings) var accountSettings
	
  var body: some View {
    Form {
      Toggle("Setting One", isOn: Binding($accountSettings.settingOne))
      Toggle("Setting Two", isOn: Binding($accountSettings.settingTwo))
      Toggle("Setting Three", isOn: Binding($accountSettings.settingThree))
    }
    .toolbar {
      if $accountSettings.isSaving {
          ProgressView()
      }
    }
  }
}

But I would like to add a progress indicator when there's an in-flight request to save, and it doesn't seem like that's possible.