Enable copy/paste/cut in macOS MSAuth web view

Add a basic application main menu bar, with 'Edit' submenu containing
the standard text manipulation commands (cut, copy, paste, select all,
delete) to enable these actions in the authentication webview.

This is useful for users who use password managers and need to paste
into the webview.

Author: mjcheetham

src/osx/Microsoft.Authentication.Helper.Mac/Source/Core/AHAppDelegate.m

@@ -2,6 +2,7 @@
 // Licensed under the MIT license.
 
 #import "AHAppDelegate.h"
+#import <Cocoa/Cocoa.h>
 
 extern const NSString* kErrorDomain;
 
@@ -21,7 +22,10 @@ -(id)initWithBlock:(AHAppWorkBlock)block logger:(AHLogger*)logger;
 
 -(void)run
 {
-    NSApplication * application = [NSApplication sharedApplication];
+    NSApplication *application = [NSApplication sharedApplication];
+    NSMenu *mainMenu = [self createMainMenu];
+    [application setMainMenu:mainMenu];
+
     [self setApplication:application];
     [application setDelegate:self];
     [NSApp setActivationPolicy:NSApplicationActivationPolicyRegular];
@@ -57,6 +61,35 @@ -(void) stop
     [[self application] postEvent:event atStart:NO];
 }
 
+-(NSMenu*) createMainMenu
+{
+    NSMenu *mainMenu = [NSMenu new];
+
+    // Create top-level menu items
+    NSMenuItem *appMenuItem = [NSMenuItem new];
+    NSMenuItem *editMenuItem = [NSMenuItem new];
+    [mainMenu addItem:appMenuItem];
+    [mainMenu addItem:editMenuItem];
+
+    // Create app menu items
+    NSMenu *appMenu = [NSMenu new];
+    [appMenuItem setSubmenu:appMenu];
+    [appMenu addItemWithTitle:@"Quit"
+                       action:@selector(terminate:)
+                keyEquivalent:@"q"];
+
+    // Create edit menu items
+    NSMenu *editMenu = [[NSMenu alloc] initWithTitle:@"Edit"];
+    [editMenuItem setSubmenu:editMenu];
+    [editMenu addItemWithTitle:@"Cut" action:@selector(cut:) keyEquivalent:@"x"];
+    [editMenu addItemWithTitle:@"Copy" action:@selector(copy:) keyEquivalent:@"c"];
+    [editMenu addItemWithTitle:@"Paste" action:@selector(paste:) keyEquivalent:@"v"];
+    [editMenu addItemWithTitle:@"Delete" action:@selector(delete:) keyEquivalent:@""];
+    [editMenu addItemWithTitle:@"Select All" action:@selector(selectAll:) keyEquivalent:@"a"];
+
+    return mainMenu;
+}
+
 + (NSError*)runDelegate:(AHAppWorkBlock)completionBlock logger:(AHLogger*)logger
 {
     AHAppDelegate * delegate = [[AHAppDelegate alloc] initWithBlock:completionBlock logger:logger];