added cookie file support (https://curl.se/libcurl/c/CURLOPT_COOKIEFILE.html) (#174)

Author: laci-aura

inc/lift/request.hpp

@@ -480,6 +480,14 @@ class request
         m_debug_info_handler = std::move(callback_functor);
     }
 
+    /**
+     * @param cookie_file The filename to read cookies from;
+     * empty string ("") enables the cookie engine without reading any initial cookies;
+     * "-" (a single minus sign) reads from stdin instead;
+     * std::nullopt disables the cookie engine and clears the list of files to read cookies from.
+     */
+    auto cookie_file(std::optional<std::filesystem::path> cookie_file) -> void { m_cookie_file = cookie_file; }
+
 private:
     /// The on complete handler callback or promise to fulfill, this is only used for async requests.
     impl::copy_but_actually_move<async_handlers_type> m_on_complete_handler{std::monostate{}};
@@ -535,6 +543,8 @@ class request
     std::optional<std::chrono::milliseconds> m_happy_eyeballs_timeout{};
     /// The debug callback functor for `debug_info_type` information.  If nullptr will not be set.
     debug_info_callback_type m_debug_info_handler{nullptr};
+    // The filename to read cookies from.
+    std::optional<std::filesystem::path> m_cookie_file;
 
     /**
      * Used by the client to set an async callback for on completion notification to the user.

src/executor.cpp

@@ -393,6 +393,9 @@ auto executor::prepare() -> void
 
     m_response.m_network_error_message[0] = '\0';
     curl_easy_setopt(m_curl_handle, CURLOPT_ERRORBUFFER, m_response.m_network_error_message);
+    // https://curl.se/libcurl/c/CURLOPT_COOKIEFILE.html
+    curl_easy_setopt(
+        m_curl_handle, CURLOPT_COOKIEFILE, m_request->m_cookie_file ? m_request->m_cookie_file->string().c_str() : nullptr);
 }
 
 auto executor::copy_curl_to_response(CURLcode curl_code) -> void