refactor: Introduce specific ElementCall error type with code

src/utils/ec-errors.ts

@@ -0,0 +1,33 @@
+/*
+Copyright 2025 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+export enum ErrorCode {
+  /**
+   * Configuration problem due to no MatrixRTC backend/SFU is exposed via .well-known and no fallback configured.
+   */
+  MISSING_LIVE_KIT_SERVICE_URL = "MISSING_LIVE_KIT_SERVICE_URL",
+  CONNECTION_LOST_ERROR = "CONNECTION_LOST_ERROR",
+  UNKNOWN_ERROR = "UNKNOWN_ERROR",
+}
+
+/**
+ * Structure for errors that occur when using ElementCall.
+ */
+export class ElementCallError extends Error {
+  public code: ErrorCode;
+
+  public constructor(message: string, code: ErrorCode) {
+    super(message);
+    this.code = code;
+  }
+}
+
+export class ConnectionLostError extends ElementCallError {
+  public constructor() {
+    super("Connection lost", ErrorCode.CONNECTION_LOST_ERROR);
+  }
+}