Add labs option to exclude unverified devices (#92)

Add a labs option which will, when set, switch into the "invisible crypto"
mode of refusing to send keys to, or decrypt messages from, devices that have
not been signed by their owner.

test/settings/controllers/DeviceIsolationModeController-test.ts

@@ -0,0 +1,33 @@
+/*
+Copyright 2024 New Vector Ltd.
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only
+Please see LICENSE files in the repository root for full details.
+*/
+
+import { AllDevicesIsolationMode, OnlySignedDevicesIsolationMode } from "matrix-js-sdk/src/crypto-api";
+
+import { stubClient } from "../../test-utils";
+import DeviceIsolationModeController from "../../../src/settings/controllers/DeviceIsolationModeController.ts";
+import { SettingLevel } from "../../../src/settings/SettingLevel";
+
+describe("DeviceIsolationModeController", () => {
+    afterEach(() => {
+        jest.resetAllMocks();
+    });
+
+    describe("tracks enabling and disabling", () => {
+        it("on sets signed device isolation mode", () => {
+            const cli = stubClient();
+            const controller = new DeviceIsolationModeController();
+            controller.onChange(SettingLevel.DEVICE, "", true);
+            expect(cli.getCrypto()?.setDeviceIsolationMode).toHaveBeenCalledWith(new OnlySignedDevicesIsolationMode());
+        });
+
+        it("off sets all device isolation mode", () => {
+            const cli = stubClient();
+            const controller = new DeviceIsolationModeController();
+            controller.onChange(SettingLevel.DEVICE, "", false);
+            expect(cli.getCrypto()?.setDeviceIsolationMode).toHaveBeenCalledWith(new AllDevicesIsolationMode(true));
+        });
+    });
+});