Migrating from v4 to v5 checks for cached app ID

* In wrappers, after an app upgrades from player to user model, if the app is not opened yet and a notification is received, there was no app ID detected and init returns early.
* Now, check for the cached app ID from v4 and use that to continue the init process. This mimics what should happen when using the native SDK directly.
* The reason this is an issue on wrappers is because when an app upgrades, the Application `onCreate` is called, without needing to open the app. However, in wrappers, the `onCreate` does not set app ID.

Author: nan-li

OneSignalSDK/onesignal/core/src/main/java/com/onesignal/core/internal/preferences/IPreferencesService.kt

@@ -177,6 +177,11 @@ object PreferencePlayerPurchasesKeys {
 object PreferenceOneSignalKeys {
     // Legacy
 
+    /**
+     * (String) The legacy app ID from SDKs prior to 5.
+     */
+    const val PREFS_LEGACY_APP_ID = "GT_APP_ID"
+
     /**
      * (String) The legacy player ID from SDKs prior to 5.
      */

OneSignalSDK/onesignal/core/src/main/java/com/onesignal/internal/OneSignalImp.kt

@@ -211,15 +211,23 @@ internal class OneSignalImp : IOneSignal, IServiceProvider {
             sessionModel = services.getService<SessionModelStore>().model
             operationRepo = services.getService<IOperationRepo>()
 
-            // initWithContext is called by our internal services/receivers/activites but they do not provide
+            var forceCreateUser = false
+
+            // initWithContext is called by our internal services/receivers/activities but they do not provide
             // an appId (they don't know it).  If the app has never called the external initWithContext
             // prior to our services/receivers/activities we will blow up, as no appId has been established.
             if (appId == null && !configModel!!.hasProperty(ConfigModel::appId.name)) {
-                Logging.warn("initWithContext called without providing appId, and no appId has been established!")
-                return false
+                val legacyAppId = getLegacyAppId()
+                if (legacyAppId == null) {
+                    Logging.warn("initWithContext called without providing appId, and no appId has been established!")
+                    return false
+                } else {
+                    Logging.debug("initWithContext: using cached legacy appId $legacyAppId")
+                    forceCreateUser = true
+                    configModel!!.appId = legacyAppId
+                }
             }
 
-            var forceCreateUser = false
             // if the app id was specified as input, update the config model with it
             if (appId != null) {
                 if (!configModel!!.hasProperty(ConfigModel::appId.name) || configModel!!.appId != appId) {
@@ -418,6 +426,16 @@ internal class OneSignalImp : IOneSignal, IServiceProvider {
         }
     }
 
+    /**
+     * Returns the cached app ID from v4 of the SDK, if available.
+     */
+    private fun getLegacyAppId(): String? {
+        return preferencesService.getString(
+            PreferenceStores.ONESIGNAL,
+            PreferenceOneSignalKeys.PREFS_LEGACY_APP_ID,
+        )
+    }
+
     private fun createAndSwitchToNewUser(
         suppressBackendOperation: Boolean = false,
         modify: (