refactor: drop redundant OSNotificationsManager pushSubscriptionId cache

OSSubscriptionModel.subscriptionId.didSet already persists to UserDefaults
on every change, so the static _pushSubscriptionId cache and its setter
were duplicating state with drift risk. Route the one caller through
OneSignalIdentifiers.subscriptionId directly. Drop the now-unused
OSUserExecutor.setPushSubscriptionId call too — the model hydration on
the line above already triggers the persistence path.

Author: nan-li

iOS_SDK/OneSignalSDK/OneSignalNotifications/OSNotificationsManager.h

@@ -121,9 +121,6 @@ NS_SWIFT_NAME(onClick(event:));
 
 @property (class, readonly) OneSignalNotificationSettings* _Nonnull osNotificationSettings;
 
-// This is set by the user module
-+ (void)setPushSubscriptionId:(NSString *_Nullable)pushSubscriptionId;
-
 + (void)handleWillShowInForegroundForNotification:(OSNotification *_Nonnull)notification completion:(OSNotificationDisplayResponse _Nonnull)completion;
 + (void)handleNotificationActionWithUrl:(NSString* _Nullable)url actionID:(NSString* _Nonnull)actionID;
 + (void)clearBadgeCount:(BOOL)fromNotifOpened fromClearAll:(BOOL)fromClearAll;

iOS_SDK/OneSignalSDK/OneSignalNotifications/OSNotificationsManager.m

@@ -232,17 +232,6 @@ + (NSString*)pushToken {
     return _pushToken;
 }
 
-static NSString *_pushSubscriptionId;
-+ (NSString*)pushSubscriptionId {
-    if (!_pushSubscriptionId) {
-        _pushSubscriptionId = OneSignalIdentifiers.subscriptionId;
-    }
-    return _pushSubscriptionId;
-}
-+ (void)setPushSubscriptionId:(NSString *)pushSubscriptionId {
-    _pushSubscriptionId = pushSubscriptionId;
-}
-
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wundeclared-selector"
 + (void)startSwizzling {
@@ -784,7 +773,7 @@ + (void)submitNotificationOpened:(NSString*)messageId {
     NSString* lastMessageId = [standardUserDefaults getSavedStringForKey:OSUD_LAST_MESSAGE_OPENED defaultValue:nil];
     //Only submit request if messageId not nil and: (lastMessage is nil or not equal to current one)
     if(messageId && (!lastMessageId || ![lastMessageId isEqualToString:messageId])) {
-        [OneSignalCoreImpl.sharedClient executeRequest:[OSRequestSubmitNotificationOpened withUserId:[self pushSubscriptionId]
+        [OneSignalCoreImpl.sharedClient executeRequest:[OSRequestSubmitNotificationOpened withUserId:OneSignalIdentifiers.subscriptionId
                                                                                              appId:[OneSignalConfigManager getAppId]
                                                                                          wasOpened:YES
                                                                                          messageId:messageId

iOS_SDK/OneSignalSDK/OneSignalUser/Source/Executors/OSUserExecutor.swift

@@ -528,11 +528,8 @@ extension OSUserExecutor {
                    areTokensEqual(tokenA: originalPushToken, tokenB: subModel["token"] as? String)
                 {
                     OneSignalUserManagerImpl.sharedInstance.pushSubscriptionModel?.hydrate(subModel)
-                    if let subId = subModel["id"] as? String {
-                        OSNotificationsManager.setPushSubscriptionId(subId)
-                        if addNewRecords {
-                            newRecordsState.add(subId)
-                        }
+                    if addNewRecords, let subId = subModel["id"] as? String {
+                        newRecordsState.add(subId)
                     }
                     break
                 }