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/error.h

@@ -0,0 +1,54 @@
+#ifndef CPR_ERROR_H
+#define CPR_ERROR_H
+
+#include <cstdint>
+#include <string>
+
+#include "cpr/cprtypes.h"
+#include <utility>
+
+namespace cpr {
+
+enum class ErrorCode {
+    OK = 0,
+    CONNECTION_FAILURE,
+    EMPTY_RESPONSE,
+    HOST_RESOLUTION_FAILURE,
+    INTERNAL_ERROR,
+    INVALID_URL_FORMAT,
+    NETWORK_RECEIVE_ERROR,
+    NETWORK_SEND_FAILURE,
+    OPERATION_TIMEDOUT,
+    PROXY_RESOLUTION_FAILURE,
+    SSL_CONNECT_ERROR,
+    SSL_LOCAL_CERTIFICATE_ERROR,
+    SSL_REMOTE_CERTIFICATE_ERROR,
+    SSL_CACERT_ERROR,
+    GENERIC_SSL_ERROR,
+    UNSUPPORTED_PROTOCOL,
+    REQUEST_CANCELLED,
+    UNKNOWN_ERROR = 1000,
+};
+
+class Error {
+  public:
+    ErrorCode code = ErrorCode::OK;
+    std::string message{};
+
+    Error() = default;
+
+    Error(const std::int32_t& curl_code, std::string&& p_error_message)
+            : code{getErrorCodeForCurlError(curl_code)},
+              message(std::move(p_error_message)) {}
+
+    explicit operator bool() const {
+        return code != ErrorCode::OK;
+    }
+
+  private:
+    static ErrorCode getErrorCodeForCurlError(std::int32_t curl_code);
+};
+
+} // namespace cpr
+
+#endif