Introduce UserServerResolver.

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

@@ -121,4 +121,10 @@ interface MatrixClient : Closeable {
      * This flow will emit a new value whenever the send queue is disabled for a room.
      */
     fun sendQueueDisabledFlow(): Flow<RoomId>
+
+    /**
+     * Return the server name part of the current user ID, using the SDK, and if a failure occurs,
+     * compute it manually.
+     */
+    fun userIdServerName(): String
 }

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

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2024 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
+ *
+ *     https://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.libraries.matrix.api.server
+
+interface UserServerResolver {
+    fun resolve(): String
+}