feat: add customer session refresh functionality and improve session management

- Introduced RealtimeCustomerSessionRefreshPayload and RealtimeCustomerSessionRefreshEvent types for handling session refresh events.
- Updated ws_service to verify customer session and handle session refresh notifications.
- Enhanced API client to manage customer session tokens and expiration.
- Implemented customer session validation and storage in session storage.
- Added functions to exchange and ensure customer sessions.
- Updated IM real-time connection to include customer session tokens in WebSocket requests.
- Modified SDK and widget configurations to support external IDs and user tokens.

web/public/sdk/cs-agent-widget.js

@@ -41,6 +41,9 @@
     merged.baseUrl = String(merged.baseUrl || window.location.origin).replace(/\/$/, "");
     merged.apiBaseUrl = String(merged.apiBaseUrl || merged.baseUrl).replace(/\/$/, "");
     merged.channelId = String(merged.channelId || "");
+    if (merged.externalId) {
+      merged.externalId = String(merged.externalId);
+    }
     if (merged.userToken) {
       merged.userToken = String(merged.userToken);
     }
@@ -66,6 +69,7 @@
     if (config.position) frameUrl.searchParams.set("position", config.position);
     if (config.themeColor) frameUrl.searchParams.set("themeColor", config.themeColor);
     if (config.width) frameUrl.searchParams.set("width", config.width);
+    if (config.externalId) frameUrl.searchParams.set("externalId", config.externalId);
     if (config.externalName) frameUrl.searchParams.set("externalName", config.externalName);
     if (config.userToken) frameUrl.searchParams.set("userToken", config.userToken);
     return frameUrl;