feat: Add PFUser.unregisterAuthenticationDelegate and allow to register delegate gracefully if another delegate is already registered (#1711)

Author: mtrezza

Parse/Parse/Internal/User/AuthenticationProviders/Controller/PFUserAuthenticationController.m

@@ -55,8 +55,13 @@ - (void)registerAuthenticationDelegate:(id<PFUserAuthenticationDelegate>)delegat
                            forAuthType:(NSString *)authType {
     PFParameterAssert(delegate, @"Authentication delegate can't be `nil`.");
     PFParameterAssert(authType, @"`authType` can't be `nil`.");
-    PFParameterAssert(![self authenticationDelegateForAuthType:authType],
-                        @"Authentication delegate already registered for authType `%@`.", authType);
+    
+    // If auth delete is already registered then unregister it gracefully
+    if ([self authenticationDelegateForAuthType:authType]) {
+        NSLog(@"unregistering existing deletegate to gracefully register new delegate for authType `%@`.", authType);
+        [self unregisterAuthenticationDelegateForAuthType:authType];
+    }
+    
     dispatch_sync(_dataAccessQueue, ^{
         self->_authenticationDelegates[authType] = delegate;
     });

Parse/Parse/Source/PFUser.h

@@ -283,7 +283,8 @@ typedef void(^PFUserLogoutResultBlock)(NSError *_Nullable error);
 ///--------------------------------------
 
 /**
- Registers a third party authentication delegate.
+ Registers a third party authentication delegate. If a delegate is already registered for the authType then
+ it is replaced by the new delegate.
 
  @note This method shouldn't be invoked directly unless developing a third party authentication library.
  @see PFUserAuthenticationDelegate
@@ -293,6 +294,16 @@ typedef void(^PFUserLogoutResultBlock)(NSError *_Nullable error);
  */
 + (void)registerAuthenticationDelegate:(id<PFUserAuthenticationDelegate>)delegate forAuthType:(NSString *)authType;
 
+/**
+ Unregisters a third party authentication delegate. If no delegate is registered, this fails gracefully.
+
+ @note This method shouldn't be invoked directly unless developing a third party authentication library.
+ @see PFUserAuthenticationDelegate
+
+ @param authType The name of the type of third party authentication source.
+ */
++ (void)unregisterAuthenticationDelegateForAuthType:(NSString *)authType;
+
 /**
  Logs in a user with third party authentication credentials.
 

Parse/Parse/Source/PFUser.m

@@ -848,6 +848,10 @@ + (void)registerAuthenticationDelegate:(id<PFUserAuthenticationDelegate>)delegat
     [[self authenticationController] registerAuthenticationDelegate:delegate forAuthType:authType];
 }
 
++ (void)unregisterAuthenticationDelegateForAuthType:(NSString *)authType {
+    [[self authenticationController] unregisterAuthenticationDelegateForAuthType:authType];
+}
+
 #pragma mark Log In
 
 + (BFTask<__kindof PFUser *> *)logInWithAuthTypeInBackground:(NSString *)authType