Add campaign parameters to the screen event (#20)

Author: mattiosdev

Sources/SegmentFirebase/FirebaseDestination.swift

@@ -116,12 +116,18 @@ public class FirebaseDestination: DestinationPlugin {
     public func screen(event: ScreenEvent) -> ScreenEvent? {
 
         if let eventName = event.name {
+            var parameters: [String: Any] = [FirebaseAnalytics.AnalyticsParameterScreenName: eventName]
+            
+            if let campaign = event.context?.dictionaryValue?["campaign"] as? [String: Any] {
+                let campaignParameters = returnMappedFirebaseParameters(campaign, for: FirebaseDestination.campaignMappedKeys)
+                parameters = parameters.merging(campaignParameters) { (current, _) in current }
+            }
+            
             FirebaseAnalytics.Analytics.logEvent(FirebaseAnalytics.AnalyticsEventScreenView,
-                                                 parameters: [FirebaseAnalytics.AnalyticsParameterScreenName: eventName])
+                                                 parameters: parameters)
             analytics?.log(message: "Firebase setScreenName \(eventName)")
         }
 
-
         return event
     }
 }