make installationIdentification KVO'able

Classes/BITAuthenticator.h

@@ -81,10 +81,11 @@ typedef void(^tValidationCompletion)(BOOL validated, NSError *error);
  *  to provide better error reporting & analytics. If authenticator is configured to login 
  *  (@see BITAuthenticatorValidationType), this identifier is retrieved from HockeyApp. In case
  *  it is disabled, it returns the vendorIdentifier provided by UIKit.
+ *  KVO'able
  *
  *	@return	a string identifying this app installation
  */
-- (NSString *) installationIdentification;
+@property (nonatomic, readonly) NSString *installationIdentification;
 
 #pragma mark - Authentication
 /**

Classes/BITAuthenticator.m

@@ -328,11 +328,13 @@ static NSString* const kBITAuthenticatorLastAuthenticatedVersionKey = @"BITAuthe
 #pragma mark - Property overrides
 - (void)setAuthenticationToken:(NSString *)authenticationToken {
   if(![self.authenticationToken isEqualToString:authenticationToken]) {
+    [self willChangeValueForKey:@"installationIdentification"];
     if(nil == authenticationToken) {
       [self removeKeyFromKeychain:kBITAuthenticatorAuthTokenKey];
     } else {
       [self addStringValueToKeychain:authenticationToken forKey:kBITAuthenticatorAuthTokenKey];
     }
+    [self didChangeValueForKey:@"installationIdentification"];
   }
 }
 

Support/HockeySDKTests/BITAuthenticatorTests.m

@@ -27,11 +27,14 @@
 - (NSString*) uniqueIdentifier {return @"reallyUnique";}
 @end
 
+static void *kInstallationIdentification = &kInstallationIdentification;
+
 @interface BITAuthenticatorTests : SenTestCase
 @end
 
 @implementation BITAuthenticatorTests {
   BITAuthenticator *_sut;
+  BOOL _KVOCalled;
 }
 
 - (void)setUp {
@@ -190,6 +193,28 @@
   assertThat(_sut.authenticationToken, equalTo(nil));
 }
 
+- (void) testThatKVOWorksOnApplicationIdentification {
+  //this will prepare everything and show the viewcontroller
+  [_sut authenticateWithCompletion:nil];
+
+  [_sut addObserver:self forKeyPath:@"installationIdentification"
+            options:0
+            context:kInstallationIdentification];
+  
+  //fake delegate call from the viewcontroller
+  [_sut authenticationViewControllerDidCancel:nil];
+  assertThatBool(_KVOCalled, equalToBool(YES));
+  [_sut removeObserver:self forKeyPath:@"installationIdentification"];
+}
+
+- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
+  if(kInstallationIdentification == context) {
+    _KVOCalled = YES;
+  } else {
+    [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];
+  }
+}
+
 #pragma mark - validation tests
 - (void) testThatValidationWithoutTokenWantsToShowTheAuthenticationViewController {
   id delegateMock = mockProtocol(@protocol(BITAuthenticatorDelegate));