WebSocket leak (#760)

Resolves #759 

Root cause: `URLSession(configuration: config, delegate: self,
delegateQueue: nil)` keeps a strong
[reference](https://developer.apple.com/documentation/foundation/urlsession/init(configuration:delegate:delegatequeue:))
to its delegate

Author: pblazej

.changes/socket-leak

@@ -0,0 +1 @@
+patch type="fixed" "Fixed WebSocket memory leak after disconnecting"

Sources/LiveKit/Support/WebSocket.swift

@@ -84,6 +84,7 @@ final class WebSocket: NSObject, @unchecked Sendable, Loggable, AsyncSequence, U
 
     func close() {
         task.cancel(with: .normalClosure, reason: nil)
+        urlSession.finishTasksAndInvalidate()
 
         _state.mutate { state in
             state.connectContinuation?.resume(throwing: LiveKitError(.cancelled))

Tests/LiveKitTests/Room/RoomTests.swift

@@ -41,6 +41,15 @@ class RoomTests: LKTestCase, @unchecked Sendable {
         }
     }
 
+    func testResourcesCleanUp() async throws {
+        try await withRooms([RoomTestingOptions()]) { rooms in
+            let room = rooms[0]
+
+            let socket = await room.signalClient._state.socket
+            self.noLeaks(of: socket!)
+        }
+    }
+
     func testSendDataPacket() async throws {
         try await withRooms([RoomTestingOptions()]) { rooms in
             let room = rooms[0]

Tests/LiveKitTests/Support/Assertions.swift

@@ -24,3 +24,11 @@ func XCTAssertThrowsErrorAsync(_ expression: @autoclosure () async throws -> som
         // Pass
     }
 }
+
+extension LKTestCase {
+    func noLeaks(of instance: AnyObject & Sendable, file: StaticString = #filePath, line: UInt = #line) {
+        addTeardownBlock { [weak instance] in
+            XCTAssertNil(instance, "Leaked object: \(String(describing: instance))", file: file, line: line)
+        }
+    }
+}