Fix: iOS call answer & hangup

CHANGELOG.md

@@ -1,5 +1,7 @@
 ## 0.3.1
 
+* Fix: [iOS] Fix `hangUp()` not ending incoming call when call is ringing. [Issue #244](https://github.com/cybex-dev/twilio_voice/issues/244)
+* Feat: [iOS] Add missing `answer()` native implementation. [Issue #244](https://github.com/cybex-dev/twilio_voice/issues/244)
 * Feat: Add raw `Connect({Map<String, dynamic>?})` for all platforms
 * Refactor: [Web] Removed unused `web_callkit` event listeners. 
 * Fix: [Web] Check if call SID is present when call is disconnected (this occurs if the call ends abruptly after starting, and `params` does not contain `CallSid`).

ios/Classes/SwiftTwilioVoicePlugin.swift

@@ -268,7 +268,14 @@ public class SwiftTwilioVoicePlugin: NSObject, FlutterPlugin,  FlutterStreamHand
             eventSink(!isOnHold ? "Hold" : "Unhold")
         }
         else if flutterCall.method == "answer" {
-            // nuthin
+            if(self.callInvite != nil) {
+                let ci = self.callInvite!
+                self.sendPhoneCallEvents(description: "LOG|answer method invoked", isError: false)
+                self.answerCall(callInvite: ci)
+            } else {
+                let ferror: FlutterError = FlutterError(code: "ANSWER_ERROR", message: "No call invite to answer", details: nil)
+                _result!(ferror)
+            }
         }
         else if flutterCall.method == "unregister" {
             guard let deviceToken = deviceToken else {
@@ -287,6 +294,8 @@ public class SwiftTwilioVoicePlugin: NSObject, FlutterPlugin,  FlutterStreamHand
                 self.userInitiatedDisconnect = true
                 performEndCallAction(uuid: self.call!.uuid!)
                 //self.toggleUIState(isEnabled: false, showCallControl: false)
+            } else if(self.callInvite != nil) {
+                performEndCallAction(uuid: self.callInvite!.uuid)
             }
         }else if flutterCall.method == "registerClient"{
             guard let clientId = arguments["id"] as? String, let clientName =  arguments["name"] as? String else {return}
@@ -368,6 +377,18 @@ public class SwiftTwilioVoicePlugin: NSObject, FlutterPlugin,  FlutterStreamHand
 
         return false;
     }
+
+    func answerCall(callInvite: CallInvite) {
+        let answerCallAction = CXAnswerCallAction(call: callInvite.uuid)
+        let transaction = CXTransaction(action: answerCallAction)
+
+        callKitCallController.request(transaction)  { error in
+            if let error = error {
+                self.sendPhoneCallEvents(description: "LOG|AnswerCallAction transaction request failed: \(error.localizedDescription)", isError: false)
+                return
+            }
+        }
+    }
 
     func makeCall(to: String)
     {