Simplify operations watcher

app/src/main/java/eu/faircode/email/TwoStateOwner.java

@@ -0,0 +1,28 @@
+package eu.faircode.email;
+
+import androidx.annotation.NonNull;
+import androidx.lifecycle.Lifecycle;
+import androidx.lifecycle.LifecycleOwner;
+import androidx.lifecycle.LifecycleRegistry;
+
+public class TwoStateOwner implements LifecycleOwner {
+    private LifecycleRegistry registry;
+
+    TwoStateOwner() {
+        registry = new LifecycleRegistry(this);
+    }
+
+    void start() {
+        registry.handleLifecycleEvent(Lifecycle.Event.ON_START);
+    }
+
+    void stop() {
+        registry.handleLifecycleEvent(Lifecycle.Event.ON_STOP);
+    }
+
+    @NonNull
+    @Override
+    public Lifecycle getLifecycle() {
+        return registry;
+    }
+}