[ios] Add enabled.telemetry key to turnstile event

Supercedes #3496

platform/ios/src/MGLMapboxEvents.m

@@ -417,37 +417,33 @@ - (void)startUpdatingLocation {
 }
 
 - (void) pushTurnstileEvent {
-
  __weak MGLMapboxEvents *weakSelf = self;
 
  dispatch_async(_serialQueue, ^{
-
  MGLMapboxEvents *strongSelf = weakSelf;
 
  if ( ! strongSelf) return;
 
- // Build only IDFV event
- NSString *vid = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
+ NSString *idfv = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
 
-  if (!vid) return;
+ if ( ! idfv) return;
 
- NSDictionary *vevt = @{
- @"event" : MGLEventTypeAppUserTurnstile,
- @"created" : [strongSelf.rfc3339DateFormatter stringFromDate:[NSDate date]],
- @"vendorId": vid,
- @"version": @(version)
- };
+ NSDictionary *vevt = @{
+ @"event" : MGLEventTypeAppUserTurnstile,
+ @"created" : [strongSelf.rfc3339DateFormatter stringFromDate:[NSDate date]],
+ @"vendorId": idfv,
+ @"version": @(version),
+ @"enabled.telemetry": @([[strongSelf class] isEnabled])
+ };
 
- // Add to Queue
- [_eventQueue addObject:vevt];
+ [_eventQueue addObject:vevt];
 
-  // Flush
-  [strongSelf flush];
+ // Flush
+ [strongSelf flush];
 
  if ([strongSelf debugLoggingEnabled]) {
  [strongSelf writeEventToLocalDebugLog:vevt];
  }
-
  });
 }
 
@@ -477,7 +473,7 @@ - (void) pushEvent:(NSString *)event withAttributes:(MGLMapboxEventAttributes *)
  return;
  }
 
- if (!event) return;
+ if ( ! event) return;
 
  MGLMutableMapboxEventAttributes *evt = [MGLMutableMapboxEventAttributes dictionaryWithDictionary:attributeDictionary];
  // Send these keys with every event