Add StartDMAction to further share code

features/createroom/api/src/main/kotlin/io/element/android/features/createroom/api/StartDMAction.kt

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2023 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.element.android.features.createroom.api
+
+import androidx.compose.runtime.MutableState
+import io.element.android.libraries.architecture.Async
+import io.element.android.libraries.matrix.api.core.RoomId
+import io.element.android.libraries.matrix.api.core.UserId
+
+interface StartDMAction {
+    /**
+     * Try to find an existing DM with the given user, or create one if none exists.
+     * @param userId The user to start a DM with.
+     * @param actionState The state to update with the result of the action.
+     */
+    suspend fun execute(userId: UserId, actionState: MutableState<Async<RoomId>>)
+}