Refactor web CLI into focused modules (#1837)

packages/web/bin/lib/cli-errors.js

@@ -0,0 +1,18 @@
+const EXIT_CODE = {
+  SUCCESS: 0,
+  GENERAL_ERROR: 1,
+  USAGE_ERROR: 2,
+  MISSING_DEPENDENCY: 3,
+  AUTH_CONFIG_ERROR: 4,
+  NETWORK_RUNTIME_ERROR: 5,
+};
+
+class TunnelCliError extends Error {
+  constructor(message, exitCode = EXIT_CODE.GENERAL_ERROR) {
+    super(message);
+    this.name = 'TunnelCliError';
+    this.exitCode = exitCode;
+  }
+}
+
+export { EXIT_CODE, TunnelCliError };