Connecting state issue fixes

On SDK configuration, interactor instance is created and has .none state. When Call screen is loaded, its start() method is called which executes some updates based on current interactor.state. When configure method is called before each engagement start (like we currently do in WidgetsSDK Testing app), CallViewModel.start() does nothing, because interactor.state is .none.
But when WidgesSDK is configured once (for example on the app launch), the same interactor instance is used for all subsequent engagements. When you end first engagement (Chat/Audio/Video, probably CV also), interactor.state is .ended. Then if you start new Audio/Video engagement, CallViewModel.start() calls CallViewModel.call.end() method, which breaks something and connecting state becomes infinite.
This commit fixes calling CallViewModel.call.end() on Audio/Video engagement start.
Commit also make two engagement references weak to avoid retaining it when CoreSDK already released it from memory.
The toggle (UISwitch) was added to Main screen, that provides the ability to disable/enable SDK configuration before each engagement.

MOB-2730

GliaWidgets/Sources/Interactor/Interactor.swift

@@ -56,7 +56,7 @@ class Interactor {
     }
 
     let configuration: Configuration
-    var currentEngagement: CoreSdkClient.Engagement?
+    weak var currentEngagement: CoreSdkClient.Engagement?
 
     /// Flag indicating if configuration was already performed.
     var isConfigurationPerformed: Bool = false

GliaWidgets/Sources/ViewModel/Call/CallViewModel.swift

@@ -72,7 +72,20 @@ class CallViewModel: EngagementViewModel, ViewModel {
         super.start()
 
         update(for: call.kind.value)
-        update(for: interactor.state)
+
+        // In the case when SDK is configured once and then
+        // visitor has several Audio/Video engagements in a raw,
+        // after ending each of them, `interactor.state` has `.ended` value,
+        // which causes calling `call.end()` on the start of the next
+        // Audio/Video engagement. That `call.end()` breaks the flow and SDK does not
+        // handle `connected` state properly. So we need to skip handling `.ended` state
+        // on the start of a new engagement.
+        switch interactor.state {
+        case .ended:
+            break
+        default:
+            update(for: interactor.state)
+        }
 
         switch startWith {
         case .engagement(let mediaType):

GliaWidgets/Sources/ViewModel/EngagementViewModel.swift

@@ -11,7 +11,7 @@ class EngagementViewModel: CommonEngagementModel {
     let alertConfiguration: AlertConfiguration
     let environment: Environment
     let screenShareHandler: ScreenShareHandler
-    var activeEngagement: CoreSdkClient.Engagement?
+    weak var activeEngagement: CoreSdkClient.Engagement?
 
     private(set) var isViewActive = ObservableValue<Bool>(with: false)
 
@@ -225,10 +225,10 @@ class EngagementViewModel: CommonEngagementModel {
     }
 
     func endSession() {
-        interactor.endSession {
-            self.engagementDelegate?(.finished)
-        } failure: { _ in
-            self.engagementDelegate?(.finished)
+        interactor.endSession { [weak self] in
+            self?.engagementDelegate?(.finished)
+        } failure: { [weak self] _ in
+            self?.engagementDelegate?(.finished)
         }
         self.screenShareHandler.stop(nil)
     }

GliaWidgetsTests/Sources/CallViewModelTests.swift

@@ -335,4 +335,16 @@ class CallViewModelTests: XCTestCase {
 
         XCTAssertEqual(call.kind.value, .audio)
     }
+
+    func test_startMethodDoesNotHandleInteractorStateEnded() {
+        let interactor: Interactor = .mock()
+        interactor.state = .ended(.byOperator)
+        let call: Call = .mock()
+        let viewModel: CallViewModel = .mock(interactor: interactor, call: call)
+
+        XCTAssertEqual(call.state.value, .none)
+        viewModel.start()
+
+        XCTAssertEqual(call.state.value, .none)
+    }
 }