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.

config/config.example.yaml

@@ -20,6 +20,14 @@ auth:
   maxFailedAttempts: 5
   credentialLockMinute: 15
 
+customerSession:
+  # 客服会话 token 签名密钥。必须使用独立高强度随机字符串，不要复用渠道 userTokenSecret。
+  secret: ""
+  # 客服会话 token 默认有效期，单位分钟。
+  ttlMinutes: 120
+  # token 剩余有效期小于该值时自动续期，单位分钟。
+  refreshThresholdMinutes: 30
+
 storage:
   default: local
   maxUploadSizeMB: 20