Sort the room member list and display member roles (#2412)

* Sort the room member list and display member roles

---------

Co-authored-by: ElementBot <benoitm+elementbot@element.io>

libraries/matrixui/src/main/kotlin/io/element/android/libraries/matrix/ui/room/RoomMemberExtensions.kt

@@ -0,0 +1,29 @@
+/*
+ * 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
+ *
+ *     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.libraries.matrix.ui.room
+
+import io.element.android.libraries.matrix.api.room.RoomMember
+
+/**
+ * Returns the name value to use when sorting room members.
+ *
+ * If the display name is not null and not empty, it is returned.
+ * Otherwise, the user ID is returned without the initial "@".
+ */
+fun RoomMember.sortingName(): String {
+    return displayName?.takeIf { it.isNotEmpty() } ?: userId.value.drop(1)
+}