Add OneSignal-Subscription-Id to Create User requests

- This was an ask of the SDK to support improved `last_active` tracking subscriptions that were actually active
- Moved the helper method to add this header out of User Update so it can be accessed also by Create User

Author: nan-li

iOS_SDK/OneSignalSDK/OneSignalUser/Source/Requests/OSRequestCreateUser.swift

@@ -48,6 +48,7 @@ class OSRequestCreateUser: OneSignalRequest, OSUserRequest {
             OneSignalLog.onesignalLog(.LL_DEBUG, message: "Cannot generate the create user request due to null app ID.")
             return false
         }
+        let _ = self.addPushSubscriptionIdToAdditionalHeaders()
         self.addJWTHeader(identityModel: identityModel)
         self.path = "apps/\(appId)/users"
         // The pushSub doesn't need to have a token.

iOS_SDK/OneSignalSDK/OneSignalUser/Source/Requests/OSRequestUpdateProperties.swift

@@ -55,17 +55,6 @@ class OSRequestUpdateProperties: OneSignalRequest, OSUserRequest {
         }
     }
 
-    func addPushSubscriptionIdToAdditionalHeaders() -> Bool {
-        if let pushSubscriptionId = OneSignalUserManagerImpl.sharedInstance.pushSubscriptionId {
-            var additionalHeaders = self.additionalHeaders ?? [String: String]()
-            additionalHeaders["OneSignal-Subscription-Id"] = pushSubscriptionId
-            self.additionalHeaders = additionalHeaders
-            return true
-        } else {
-            return false
-        }
-    }
-
     init(properties: [String: Any], deltas: [String: Any]?, refreshDeviceMetadata: Bool?, modelToUpdate: OSPropertiesModel, identityModel: OSIdentityModel) {
         self.modelToUpdate = modelToUpdate
         self.identityModel = identityModel

iOS_SDK/OneSignalSDK/OneSignalUser/Source/Requests/OSUserRequest.swift

@@ -41,4 +41,16 @@ internal extension OneSignalRequest {
 //        additionalHeaders["Authorization"] = "Bearer \(token)"
 //        self.additionalHeaders = additionalHeaders
     }
+    
+    /** Returns if the `OneSignal-Subscription-Id` header was added successfully. */
+    func addPushSubscriptionIdToAdditionalHeaders() -> Bool {
+        if let pushSubscriptionId = OneSignalUserManagerImpl.sharedInstance.pushSubscriptionId {
+            var additionalHeaders = self.additionalHeaders ?? [String: String]()
+            additionalHeaders["OneSignal-Subscription-Id"] = pushSubscriptionId
+            self.additionalHeaders = additionalHeaders
+            return true
+        } else {
+            return false
+        }
+    }
 }