Fixes invalid memory access

std::string_view causes invalid memory access in multipart branch when
assigned local variable goes out of scope and string_view is passed to
ramAuthenticateUser. Moved MultipartParser to higher scope, to ensure
it is not deleted before std::string_view.

Tested:
  - Executed post on /login, got response:
    {
      "data": "User 'root' logged in",
      "message": "200 OK",
      "status": "ok"
    }

Change-Id: I0b02dddcb1a887d442525ffedb7a08a00087f2f2
Signed-off-by: Krzysztof Grobelny <krzysztof.grobelny@intel.com>
diff --git a/include/login_routes.hpp b/include/login_routes.hpp
index fd1c357..0ff313c 100644
--- a/include/login_routes.hpp
+++ b/include/login_routes.hpp
@@ -24,6 +24,7 @@
         .methods(boost::beast::http::verb::post)(
             [](const crow::Request& req,
                const std::shared_ptr<bmcweb::AsyncResp>& asyncResp) {
+        MultipartParser parser;
         std::string_view contentType = req.getHeaderValue("content-type");
         std::string_view username;
         std::string_view password;
@@ -119,7 +120,6 @@
         else if (contentType.starts_with("multipart/form-data"))
         {
             looksLikePhosphorRest = true;
-            MultipartParser parser;
             ParserError ec = parser.parse(req);
             if (ec != ParserError::PARSER_SUCCESS)
             {