feat：定义 OpenAi 统一接口

src/main/java/cn/bugstack/chatglm/IOpenAiApi.java

+package cn.bugstack.chatglm;
+
+import cn.bugstack.chatglm.model.ChatCompletionRequest;
+import cn.bugstack.chatglm.model.ChatCompletionResponse;
+import io.reactivex.Single;
+import retrofit2.http.Body;
+import retrofit2.http.POST;
+import retrofit2.http.Path;
+
+/**
+ * @author 小傅哥，微信：fustack
+ * @description OpenAi 接口，用于扩展通用类服务
+ * @github https://github.com/fuzhengwei
+ * @Copyright 公众号：bugstack虫洞栈 | 博客：https://bugstack.cn - 沉淀、分享、成长，让自己和他人都能有所收获！
+ */
+public interface IOpenAiApi {
+
+    String v3_completions = "api/paas/v3/model-api/{model}/sse-invoke";
+
+    @POST(v3_completions)
+    Single<ChatCompletionResponse> completions(@Path("model") String model, @Body ChatCompletionRequest chatCompletionRequest);
+
+}