StartDM : add tests

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/MatrixClient.kt

@@ -41,7 +41,7 @@ interface MatrixClient : Closeable {
     val roomListService: RoomListService
     val mediaLoader: MatrixMediaLoader
     suspend fun getRoom(roomId: RoomId): MatrixRoom?
-    suspend fun findDM(userId: UserId): MatrixRoom?
+    suspend fun findDM(userId: UserId): RoomId?
     suspend fun ignoreUser(userId: UserId): Result<Unit>
     suspend fun unignoreUser(userId: UserId): Result<Unit>
     suspend fun createRoom(createRoomParams: CreateRoomParameters): Result<RoomId>

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/room/StartDM.kt

@@ -24,11 +24,9 @@ import io.element.android.libraries.matrix.api.core.UserId
  * Try to find an existing DM with the given user, or create one if none exists.
  */
 suspend fun MatrixClient.startDM(userId: UserId): StartDMResult {
-    val existingRoomId = findDM(userId)?.use { existingDM ->
-        existingDM.roomId
-    }
-    return if (existingRoomId != null) {
-        StartDMResult.Success(existingRoomId, isNew = false)
+    val existingDM = findDM(userId)
+    return if (existingDM != null) {
+        StartDMResult.Success(existingDM, isNew = false)
     } else {
         createDM(userId).fold(
             { StartDMResult.Success(it, isNew = true) },