feat: Adds graceful shutdown to services

Tests/MQTTConnectionServiceTests/MQTTConnectionServiceTests.swift

@@ -1,5 +1,6 @@
-import EnvVars
+import Combine
 import Logging
+import Models
 @testable import MQTTConnectionService
 import MQTTNIO
 import NIO
@@ -25,6 +26,8 @@ final class MQTTConnectionServiceTests: XCTestCase {
       try await Task.sleep(for: .seconds(1))
       XCTAssert(client.isActive())
       trigger.triggerGracefulShutdown()
+      // try await Task.sleep(for: .seconds(2))
+      // XCTAssertFalse(client.isActive())
     }
   }
 
@@ -55,4 +58,65 @@ final class MQTTConnectionServiceTests: XCTestCase {
     )
   }
 
+  func testEventStream() async throws {
+    var connection: ConnectionStream? = ConnectionStream()
+
+    let task = Task {
+      guard let events = connection?.events else { return }
+      print("before loop")
+      for await event in events {
+        print("\(event)")
+      }
+      print("after loop")
+    }
+
+    let ending = Task {
+      try await Task.sleep(for: .seconds(2))
+      connection = nil
+    }
+
+    connection?.start()
+    try await ending.value
+    task.cancel()
+  }
+
+}
+
+class ConnectionStream {
+
+  enum Event {
+    case connected
+    case disconnected
+    case shuttingDown
+  }
+
+  let events: AsyncStream<Event>
+  private let continuation: AsyncStream<Event>.Continuation
+  private var cancellable: AnyCancellable?
+
+  init() {
+    let (stream, continuation) = AsyncStream.makeStream(of: Event.self)
+    self.events = stream
+    self.continuation = continuation
+  }
+
+  deinit {
+    print("connection stream is gone.")
+    stop()
+  }
+
+  func start() {
+    cancellable = Timer.publish(every: 1.0, on: .main, in: .common)
+      .autoconnect()
+      .sink { [weak self] _ in
+        print("will send event.")
+        self?.continuation.yield(.connected)
+      }
+  }
+
+  func stop() {
+    continuation.yield(.shuttingDown)
+    cancellable = nil
+    continuation.finish()
+  }
 }