Refine online help feature

This change gives a namespace to the 'showonlinehelp' message type, making
it 'powerShell/showOnlineHelp'.  Also changes the request parameter type
to a string and uses PSCommand.AddCommand, etc to avoid script injection
attacks.

Author: daviwil

src/PowerShellEditorServices.Host/LanguageServer.cs

@@ -135,20 +135,19 @@ protected Task HandleShutdownRequest(
         }
 
         protected async Task HandleShowOnlineHelpRequest(
-            object helpParams,
+            string helpParams,
             EditorSession editorSession,
             RequestContext<object, object> requestContext)
         {
-            var psCommand = new PSCommand();
-
             if (helpParams == null) { helpParams = "get-help"; }
 
-            var script = string.Format("get-help {0} -Online", helpParams);
-
-            psCommand.AddScript(script);
+            var psCommand = new PSCommand();
+            psCommand.AddCommand("Get-Help");
+            psCommand.AddArgument(helpParams);
+            psCommand.AddParameter("Online");
 
-            var result = await editorSession.PowerShellContext.ExecuteCommand<object>(
-                        psCommand);
+            await editorSession.PowerShellContext.ExecuteCommand<object>(
+                    psCommand);
 
             await requestContext.SendResult(null);
         }

src/PowerShellEditorServices.Protocol/LanguageServer/ShowOnlineHelpRequest.cs

@@ -9,6 +9,8 @@ namespace Microsoft.PowerShell.EditorServices.Protocol.LanguageServer
 {
     public class ShowOnlineHelpRequest
     {
-        public static readonly RequestType<object, object, object> Type = RequestType<object, object, object>.Create("showonlinehelp");
+        public static readonly 
+            RequestType<string, object, object> Type = 
+            RequestType<string, object, object>.Create("powerShell/showOnlineHelp");
     }
 }