Avoid unused warning

[heifner]

Workaround unused compiler warning. Note [[maybe_unused]] does not work for lambda captures.

[spoonincode]

http is only used for a single INVOKE so I think it might be cleaner to

--- a/plugins/producer_api_plugin/producer_api_plugin.cpp
+++ b/plugins/producer_api_plugin/producer_api_plugin.cpp
@@ -23,7 +23,7 @@ using namespace eosio;
 #define CALL_WITH_400(api_name, category, api_handle, call_name, INVOKE, http_response_code) \
 {std::string("/v1/" #api_name "/" #call_name), \
    api_category::category, \
-   [&http, &producer](string&&, string&& body, url_response_callback&& cb) mutable { \
+   [&producer](string&&, string&& body, url_response_callback&& cb) mutable { \
           try { \
              INVOKE \
              cb(http_response_code, fc::variant(result)); \
@@ -63,7 +63,7 @@ using namespace eosio;
      auto result = api_handle.call_name(std::move(params));

 #define INVOKE_R_R_D(api_handle, call_name, in_param) \
-     const fc::microseconds http_max_response_time = http.get_max_response_time(); \
+     const fc::microseconds http_max_response_time = app().get_plugin<http_plugin>().get_max_response_time(); \
      auto deadline = http_max_response_time == fc::microseconds::maximum() ? fc::time_point::maximum() \
                                                                            : fc::time_point::now() + http_max_response_time; \
      auto params = parse_params<in_param, http_params_types::possible_no_params>(body);\
@@ -91,7 +91,6 @@ void producer_api_plugin::plugin_startup() {
    ilog("starting producer_api_plugin");
    // lifetime of plugin is lifetime of application
    auto& producer = app().get_plugin<producer_plugin>();
-   auto& http = app().get_plugin<http_plugin>();

    app().get_plugin<http_plugin>().add_api({
        CALL_WITH_400(producer, producer_ro, producer, paused,

[ericpassmore]

Note:start
group: CLEANCODE
category: INTERNALS
summary: Workaround to avoid unused compiler warning.
Note: end