feat:更新api模块

lib/apis/session.dart

@@ -0,0 +1,10 @@
+import 'package:food_hub_app/models/session.dart';
+import 'package:food_hub_app/utils/http_util.dart';
+
+Future<Session> loginApi(String username, String password) {
+  return HttpUtil().post<Session>(
+    "/session",
+    queryParameters: {"username": username, "password": password},
+    converter: (data) => Session.fromJson(data),
+  );
+}