kaizen: add more docs

Author: hakonk

README.md

@@ -251,43 +251,39 @@ your `Info.plist` as follows:
 
 ##### Define openURL callback in AppDelegate
 
-You need to have a property in your AppDelegate to hold the auth session, in order to continue the
-authorization flow from the redirect. To add this, open `AppDelegate.h` in your project and add the
-following lines:
+You need to retain the auth session, in order to continue the
+authorization flow from the redirect. Follow these steps: 
 
-```diff
-+ @protocol OIDAuthorizationFlowSession;
+`RNAppAuth` will call on the given app's delegate via `[UIApplication sharedApplication].delegate`.
+Furthermore, `RNAppAuth` expects the delegate instance to conform to the protocol `RNAppAuthAuthorizationFlowManager`.
+Make `AppDelegate` conform to `RNAppAuthAuthorizationFlowManager`:
 
-  @interface AppDelegate : UIResponder <UIApplicationDelegate>
-+ @property(nonatomic, strong, nullable) id<OIDAuthorizationFlowSession> currentAuthorizationFlow;
-  @property (nonatomic, strong) UIWindow *window;
-  @end
+```diff
++ @interface AppDelegate()<RNAppAuthAuthorizationFlowManager> {
++  id <OIDAuthorizationFlowSession> _currentSession;
++ }
++ @end
 ```
 
-The authorization response URL is returned to the app via the iOS openURL app delegate method, so
-you need to pipe this through to the current authorization session (created in the previous
-instruction).
-
-##### Add a current Authorization session
-
-To do this, open `AppDelegate.m` and add an import statement:
+Implement the required method of `RNAppAuthAuthorizationFlowManager` in `AppDelegate`:
 
-```Objective-C
-#import <AppAuth/AppAuth.h>
+```diff
++ -(void)setCurrentAuthorizationFlowSession:(id<OIDAuthorizationFlowSession>)session {
++    // retain session for further use
++    _currentSession = session;
++ }
 ```
 
-And in the bottom of the class, add the following handler:
+The authorization response URL is returned to the app via the iOS openURL app delegate method, so
+you need to pipe this through to the current authorization session (created in the previous
+instruction). Thus, implement the following method from `UIApplicationDelegate` in `AppDelegate`:
 
-```Objective-C
-- (BOOL)application:(UIApplication *)app
-            openURL:(NSURL *)url
-            options:(NSDictionary<NSString *, id> *)options {
-  if ([_currentAuthorizationFlow resumeAuthorizationFlowWithURL:url]) {
-    _currentAuthorizationFlow = nil;
-    return YES;
-  }
-  return NO;
-}
+```diff
++ - (BOOL)application:(UIApplication *)app openURL:(NSURL *)url options:(NSDictionary<NSString *, id> *)options {
++   BOOL shouldOpenUrl = [_currentSession resumeAuthorizationFlowWithURL:url];
++   _currentSession = nil;
++   return shouldOpenUrl;
++ }
 ```
 
 #### Integration of the library with a Swift iOS project