add plugin: ai-statistics (#1011)

plugins/wasm-go/extensions/ai-statistics/README.md

@@ -0,0 +1,44 @@
+# 介绍
+提供AI可观测基础能力，其后需接ai-proxy插件，如果不接ai-proxy插件的话，则只支持openai协议。
+
+# 配置说明
+
+| 名称         | 数据类型   | 填写要求 | 默认值 | 描述               |
+|------------|--------|------|-----|------------------|
+| `enable` | bool | 必填   | -   | 是否开启ai统计功能 |
+
+开启后 metrics 示例：
+```
+route_upstream_model_input_token{ai_route="openai",ai_cluster="qwen",ai_model="qwen-max"} 21
+route_upstream_model_output_token{ai_route="openai",ai_cluster="qwen",ai_model="qwen-max"} 17
+```
+
+日志示例：
+
+```json
+{
+    "model": "qwen-max",
+    "input_token": "21",
+    "output_token": "17",
+    "authority": "dashscope.aliyuncs.com",
+    "bytes_received": "336",
+    "bytes_sent": "1675",
+    "duration": "1590",
+    "istio_policy_status": "-",
+    "method": "POST",
+    "path": "/v1/chat/completions",
+    "protocol": "HTTP/1.1",
+    "request_id": "5895f5a9-e4e3-425b-98db-6c6a926195b7",
+    "requested_server_name": "-",
+    "response_code": "200",
+    "response_flags": "-",
+    "route_name": "openai",
+    "start_time": "2024-06-18T09:37:14.078Z",
+    "trace_id": "-",
+    "upstream_cluster": "qwen",
+    "upstream_service_time": "496",
+    "upstream_transport_failure_reason": "-",
+    "user_agent": "PostmanRuntime/7.37.3",
+    "x_forwarded_for": "-"
+}
+```