Add setLanguage method in OneSignal implementation

* Add setLanguage method in OneSignal implementation
* Add LanguageContext static variable to store current language strategy
* Initialize languageContext in OneSignal.init
* Store language from languageContext strategy in userState.language
* Add language to languageProviderAppDefined in setLanguage method and set languageContext strategy to languageProviderAppDefined

Author: tanaynigam

iOS_SDK/OneSignalSDK/Source/OneSignal.h

@@ -563,6 +563,10 @@ typedef void (^OSSMSSuccessBlock)(NSDictionary *results);
 + (void)logoutSMSNumber;
 + (void)logoutSMSNumberWithSuccess:(OSSMSSuccessBlock _Nullable)successBlock withFailure:(OSSMSFailureBlock _Nullable)failureBlock;
 
+#pragma mark Language
+
++ (void)setLanguage:(NSString * _Nonnull)language;
+
 #pragma mark External User Id
 // Typedefs defining completion blocks for updating the external user id
 typedef void (^OSUpdateExternalUserIdFailureBlock)(NSError *error);

iOS_SDK/OneSignalSDK/Source/OneSignal.m

@@ -90,6 +90,9 @@
 #import "OneSignalLifecycleObserver.h"
 #import "OSPlayerTags.h"
 
+#import "Language/LanguageProviderAppDefined.h"
+#import "Language/LanguageContext.h"
+
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wundeclared-selector"
 
@@ -188,6 +191,7 @@ + (DelayedConsentInitializationParameters *)delayedInitParameters {
 
 static OneSignalTrackIAP* trackIAPPurchase;
 NSString* emailToSet;
+static LanguageContext* languageContext;
 
 int mLastNotificationTypes = -1;
 static int mSubscriptionStatus = -1;
@@ -722,6 +726,8 @@ + (void)init {
         appId = nil;
         return;
     }
+    
+    languageContext = [LanguageContext new];
 
     [OneSignalCacheCleaner cleanCachedUserData];
     [OneSignal checkIfApplicationImplementsDeprecatedMethods];
@@ -1781,9 +1787,7 @@ + (OSUserState *)createUserState {
         userState.iOSBundle = [[NSBundle mainBundle] bundleIdentifier];
     }
 
-    let preferredLanguages = [NSLocale preferredLanguages];
-    if (preferredLanguages && preferredLanguages.count > 0)
-        userState.language = [preferredLanguages objectAtIndex:0];
+    userState.language = [languageContext language];
 
     let notificationTypes = [self getNotificationTypes];
     mLastNotificationTypes = notificationTypes;
@@ -2694,6 +2698,12 @@ + (id)getTriggerValueForKey:(NSString *)key {
     return [OSMessagingController.sharedInstance getTriggerValueForKey:key];
 }
 
++ (void)setLanguage:(NSString * _Nonnull)language {
+    let languageProviderAppDefined = [LanguageProviderAppDefined new];
+    [languageProviderAppDefined setLanguage:language];
+    [languageContext setStrategy:languageProviderAppDefined];
+    
+}
 + (void)setExternalUserId:(NSString * _Nonnull)externalId {
 
     // return if the user has not granted privacy permissions