Implement new method to enable app session customization on iOS (davide-scalzo#133)

Author: andrejunges

RNMixpanel/Mixpanel.h

@@ -201,17 +201,31 @@
 
 /*!
  @property
- 
+
  @abstract
  If set, determines the background color of mini notifications.
 
  @discussion
- If this isn't set, we default to either the color of the UINavigationBar of the top 
- UINavigationController that is showing when the notification is presented, the 
+ If this isn't set, we default to either the color of the UINavigationBar of the top
+ UINavigationController that is showing when the notification is presented, the
  UINavigationBar default color for the app or the UITabBar default color.
  */
 @property (atomic) UIColor* miniNotificationBackgroundColor;
 
+/*!
+  @property
+
+  The minimum session duration (ms) that is tracked in automatic events.
+ */
+@property (atomic) UInt64 minimumSessionDuration;
+
+/*!
+  @property
+
+  The maximum session duration (ms) that is tracked in automatic events.
+ */
+@property (atomic) UInt64 maximumSessionDuration;
+
 /*!
  @property
 
@@ -556,10 +570,10 @@
 
 /*!
  @method
- 
+
  @abstract
  Calls flush, then optionally archives and calls a handler when finished.
- 
+
  @discussion
  When calling <code>flush</code> manually, it is sometimes important to verify
  that the flush has finished before further action is taken. This is

RNMixpanel/RNMixpanel.m

@@ -46,6 +46,20 @@ -(Mixpanel*) getInstance: (NSString *)name {
     }
 }
 
+// setAppSessionProperties iOS
+RCT_EXPORT_METHOD(setAppSessionPropertiesIOS:(NSDictionary *)properties) {
+    if ([properties objectForKey:@"minimumSessionDuration"]) {
+        NSNumber *minimumSessionDuration = properties[@"minimumSessionDuration"];
+        long long int intValue = [minimumSessionDuration longLongValue];
+        mixpanel.minimumSessionDuration = intValue;
+    }
+
+    if ([properties objectForKey:@"maximumSessionDuration"]) {
+        NSNumber *maximumSessionDuration = properties[@"maximumSessionDuration"];
+        long long int intValue = [maximumSessionDuration longLongValue];
+        mixpanel.maximumSessionDuration = intValue;
+    }
+}
 
 // get distinct id
 RCT_EXPORT_METHOD(getDistinctId:(NSString *)apiToken