Enable detekt rules OptionalUnit and fix existing issues.

appnav/src/main/kotlin/io/element/android/appnav/LoggedInFlowNode.kt

@@ -100,13 +100,13 @@ class LoggedInFlowNode @AssistedInject constructor(
 ) {
 
     interface Callback : Plugin {
-        fun onOpenBugReport() = Unit
+        fun onOpenBugReport()
     }
 
     interface LifecycleCallback : NodeLifecycleCallback {
-        fun onFlowCreated(identifier: String, client: MatrixClient) = Unit
+        fun onFlowCreated(identifier: String, client: MatrixClient)
 
-        fun onFlowReleased(identifier: String, client: MatrixClient) = Unit
+        fun onFlowReleased(identifier: String, client: MatrixClient)
     }
 
     data class Inputs(

appnav/src/main/kotlin/io/element/android/appnav/room/RoomLoadedFlowNode.kt

@@ -75,8 +75,8 @@ class RoomLoadedFlowNode @AssistedInject constructor(
     }
 
     interface LifecycleCallback : NodeLifecycleCallback {
-        fun onFlowCreated(identifier: String, room: MatrixRoom) = Unit
-        fun onFlowReleased(identifier: String, room: MatrixRoom) = Unit
+        fun onFlowCreated(identifier: String, room: MatrixRoom)
+        fun onFlowReleased(identifier: String, room: MatrixRoom)
     }
 
     data class Inputs(

features/invitelist/impl/src/main/kotlin/io/element/android/features/invitelist/impl/InviteListPresenter.kt

@@ -152,8 +152,7 @@ class InviteListPresenter @Inject constructor(
             client.getRoom(roomId)?.use {
                 it.leave().getOrThrow()
                 notificationDrawerManager.clearMembershipNotificationForRoom(client.sessionId, roomId)
-            }
-            Unit
+            }.let { }
         }.runCatchingUpdatingState(declinedAction)
     }
 

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/MessagesView.kt

@@ -125,8 +125,9 @@ fun MessagesView(
         state.eventSink(MessagesEvents.ToggleReaction(emoji, event.eventId))
     }
 
-    fun onMoreReactionsClicked(event: TimelineItem.Event): Unit =
+    fun onMoreReactionsClicked(event: TimelineItem.Event) {
         state.customReactionState.eventSink(CustomReactionEvents.UpdateSelectedEvent(event.eventId))
+    }
 
     Scaffold(
         modifier = modifier,

tools/detekt/detekt.yml

@@ -54,6 +54,8 @@ style:
     active: true
   UseCheckOrError:
     active: true
+  OptionalUnit:
+    active: true
 
 coroutines:
   GlobalCoroutineUsage: