ios: try to leave the meeting when the app is terminating

Fixes: https://github.com/jitsi/jitsi-meet/issues/6665

ios/app/src/AppDelegate.m

 #import "AppDelegate.h"
 #import "FIRUtilities.h"
 #import "Types.h"
+#import "ViewController.h"
 
 @import Crashlytics;
 @import Fabric;
     return YES;
 }
 
+- (void) applicationWillTerminate:(UIApplication *)application {
+    NSLog(@"Application will terminate!");
+    // Try to leave the current meeting graceefully.
+    ViewController *rootController = (ViewController *)self.window.rootViewController;
+    [rootController terminate];
+}
+
 #pragma mark Linking delegate methods
 
 -    (BOOL)application:(UIApplication *)application

ios/app/src/ViewController.h

 
 @interface ViewController : UIViewController<JitsiMeetViewDelegate>
 
+- (void)terminate;
+
 @end

ios/app/src/ViewController.m

 }
 #endif
 
+#pragma mark - Helpers
+
+- (void)terminate {
+    JitsiMeetView *view = (JitsiMeetView *) self.view;
+    [view leave];
+}
+
 @end