feat: add base implementation for realtime communication

Signed-off-by: Philip Molares <philip.molares@udo.edu>
Signed-off-by: Erik Michelson <github@erik.michelson.eu>
Co-authored-by: Erik Michelson <github@erik.michelson.eu>
Co-authored-by: Philip Molares <philip.molares@udo.edu>
Co-authored-by: Tilman Vatteroth <git@tilmanvatteroth.de>
Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>

src/realtime/realtime-note/test-utils/mock-connection.ts

@@ -0,0 +1,22 @@
+/*
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+import { Mock } from 'ts-mockery';
+
+import { User } from '../../../users/user.entity';
+import { WebsocketConnection } from '../websocket-connection';
+
+/**
+ * Provides a partial mock for {@link WebsocketConnection}.
+ *
+ * @param synced Defines the return value for the `isSynced` function.
+ */
+export function mockConnection(synced: boolean): WebsocketConnection {
+  return Mock.of<WebsocketConnection>({
+    isSynced: jest.fn(() => synced),
+    send: jest.fn(),
+    getUser: jest.fn(() => Mock.of<User>({ username: 'mockedUser' })),
+  });
+}