Add HS capability check

libraries/slashcommands/impl/src/main/kotlin/io/element/android/libraries/slashcommands/impl/DefaultSlashCommandService.kt

@@ -99,6 +99,14 @@ class DefaultSlashCommandService(
     override suspend fun proceedAdmin(
         slashCommand: SlashCommand.SlashCommandAdmin,
     ): Result<Unit> {
+        if (slashCommand is SlashCommand.ChangeDisplayNameForRoom) {
+            val canUserChangeDisplayName = withTimeoutOrNull(5.seconds) {
+                capabilitiesProvider.canChangeDisplayName().getOrNull()
+            } ?: false
+            if (!canUserChangeDisplayName) {
+                return Result.failure(Exception("Changing display name is not allowed"))
+            }
+        }
         return commandExecutor.proceedAdmin(
             slashCommand = slashCommand,
         )