Major plugin refactor and cleanup.

Switched to POCO library for unified platform/library interface.
Deprecated the external module API. It was creating more problems than solving.
Removed most built-in libraries in favor of system libraries for easier maintenance.
Cleaned and secured code with help from static analyzers.

vendor/CPR/include/cpr/response.h

@@ -0,0 +1,56 @@
+#ifndef CPR_RESPONSE_H
+#define CPR_RESPONSE_H
+
+#include <cassert>
+#include <cstdint>
+#include <curl/curl.h>
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "cpr/cookies.h"
+#include "cpr/cprtypes.h"
+#include "cpr/error.h"
+#include "cpr/ssl_options.h"
+#include "cpr/util.h"
+
+namespace cpr {
+
+class Response {
+  protected:
+    std::shared_ptr<CurlHolder> curl_{nullptr};
+
+  public:
+    // Ignored here since libcurl uses a long for this.
+    // NOLINTNEXTLINE(google-runtime-int)
+    long status_code{};
+    std::string text{};
+    Header header{};
+    Url url{};
+    double elapsed{};
+    Cookies cookies{};
+    Error error{};
+    std::string raw_header{};
+    std::string status_line{};
+    std::string reason{};
+    cpr_off_t uploaded_bytes{};
+    cpr_off_t downloaded_bytes{};
+    // Ignored here since libcurl uses a long for this.
+    // NOLINTNEXTLINE(google-runtime-int)
+    long redirect_count{};
+
+    Response() = default;
+    Response(std::shared_ptr<CurlHolder> curl, std::string&& p_text, std::string&& p_header_string,
+             Cookies&& p_cookies, Error&& p_error);
+    std::vector<std::string> GetCertInfo();
+    Response(const Response& other) = default;
+    Response(Response&& old) noexcept = default;
+    ~Response() noexcept = default;
+
+    Response& operator=(Response&& old) noexcept = default;
+    Response& operator=(const Response& other) = default;
+};
+} // namespace cpr
+
+#endif