Record entire context for every event.

Previously, some pieces of context were set on the batch (static
context such as library info, device info, etc.).

This had the advantage of reducing the payload size (send it once
instead of 20 times in 20 event batch). But by adding gzip support we
don't really need to do this as much anymore.

So now we store the entire context with every payload, which represents the
context at the time of the event (rather than upload) more accurately.

Pod/Classes/Internal/SEGSegmentIntegration.m

@@ -52,7 +52,7 @@ static BOOL GetAdTrackingEnabled()
 @interface SEGSegmentIntegration ()
 
 @property (nonatomic, strong) NSMutableArray *queue;
-@property (nonatomic, strong) NSDictionary *context;
+@property (nonatomic, strong) NSDictionary *cachedStaticContext;
 @property (nonatomic, strong) NSArray *batch;
 @property (nonatomic, strong) SEGAnalyticsRequest *request;
 @property (nonatomic, assign) UIBackgroundTaskIdentifier flushTaskID;
@@ -79,7 +79,7 @@ - (id)initWithAnalytics:(SEGAnalytics *)analytics
         self.bluetooth = [[SEGBluetooth alloc] init];
         self.reachability = [SEGReachability reachabilityWithHostname:@"google.com"];
         [self.reachability startNotifier];
-        self.context = [self staticContext];
+        self.cachedStaticContext = [self staticContext];
         self.flushTimer = [NSTimer scheduledTimerWithTimeInterval:30.0 target:self selector:@selector(flush) userInfo:nil repeats:YES];
         self.serialQueue = seg_dispatch_queue_create_specific("io.segment.analytics.segmentio", DISPATCH_QUEUE_SERIAL);
         self.flushTaskID = UIBackgroundTaskInvalid;
@@ -192,8 +192,6 @@ - (NSDictionary *)liveContext
 {
     NSMutableDictionary *context = [[NSMutableDictionary alloc] init];
 
-    [context addEntriesFromDictionary:self.context];
-
     context[@"locale"] = [NSString stringWithFormat:
                                        @"%@-%@",
                                        [NSLocale.currentLocale objectForKey:NSLocaleLanguageCode],
@@ -346,7 +344,7 @@ - (void)registeredForRemoteNotificationsWithDeviceToken:(NSData *)deviceToken
     for (NSUInteger i = 0; i < deviceToken.length; i++) {
         [token appendString:[NSString stringWithFormat:@"%02lx", (unsigned long)buffer[i]]];
     }
-    [self.context[@"device"] setObject:[token copy] forKey:@"token"];
+    [self.cachedStaticContext[@"device"] setObject:[token copy] forKey:@"token"];
 }
 
 #pragma mark - Queueing
@@ -384,11 +382,13 @@ - (void)enqueueAction:(NSString *)action dictionary:(NSMutableDictionary *)paylo
 
         [payload setValue:[self integrationsDictionary:integrations] forKey:@"integrations"];
 
-        NSDictionary *defaultContext = [self liveContext];
+        NSDictionary *staticContext = self.cachedStaticContext;
+        NSDictionary *liveContext = [self liveContext];
         NSDictionary *customContext = context;
-        NSMutableDictionary *context = [NSMutableDictionary dictionaryWithCapacity:customContext.count + defaultContext.count];
-        [context addEntriesFromDictionary:defaultContext];
-        [context addEntriesFromDictionary:customContext]; // let the custom context override ours
+        NSMutableDictionary *context = [NSMutableDictionary dictionaryWithCapacity:(staticContext.count + liveContext.count + customContext.count)];
+        [context addEntriesFromDictionary:staticContext];
+        [context addEntriesFromDictionary:liveContext];
+        [context addEntriesFromDictionary:customContext];
         [payload setValue:[context copy] forKey:@"context"];
 
         SEGLog(@"%@ Enqueueing action: %@", self, payload);
@@ -402,7 +402,6 @@ - (void)queuePayload:(NSDictionary *)payload
         [self.queue addObject:payload];
         [[self.queue copy] writeToURL:[self queueURL] atomically:YES];
         [self flushQueueByLength];
-
     }
     @catch (NSException *exception) {
         SEGLog(@"%@ Error writing payload: %@", self, exception);
@@ -415,7 +414,6 @@ - (void)queuePayloadFromArray:(NSArray *)payloadArray
         [self.queue addObjectsFromArray:payloadArray];
         [[self.queue copy] writeToURL:[self queueURL] atomically:YES];
         [self flushQueueByLength];
-
     }
     @catch (NSException *exception) {
         SEGLog(@"%@ Error writing payload: %@", self, exception);
@@ -447,7 +445,6 @@ - (void)flushWithMaxSize:(NSUInteger)maxBatchSize
         NSMutableDictionary *payloadDictionary = [[NSMutableDictionary alloc] init];
         [payloadDictionary setObject:self.configuration.writeKey forKey:@"writeKey"];
         [payloadDictionary setObject:iso8601FormattedString([NSDate date]) forKey:@"sentAt"];
-        [payloadDictionary setObject:self.context forKey:@"context"];
         [payloadDictionary setObject:self.batch forKey:@"batch"];
 
         SEGLog(@"Flushing payload %@", payloadDictionary);