Support error code to string conversions

CMakeLists.txt

@@ -162,7 +162,7 @@ if(USE_BUNDLED_COEURL)
 	FetchContent_Declare(
 		coeurl
 		GIT_REPOSITORY https://nheko.im/Nheko-Reborn/coeurl.git
-		GIT_TAG        3901507db25cf3f9364b58cd8c7880640900c992
+		GIT_TAG        3d6555e8371702a3efd5b07a0a67918f1d46e2e6
 		)
 	FetchContent_MakeAvailable(coeurl)
 	target_link_libraries(matrix_client PUBLIC coeurl::coeurl)

include/mtxclient/http/client_impl.hpp

@@ -122,7 +122,7 @@ mtx::http::Client::prepare_callback(HeadersCallback<Response> callback)
                                      int err_code,
                                      int status_code) {
         Response response_data;
-        mtx::http::ClientError client_error;
+        mtx::http::ClientError client_error{};
 
         if (err_code) {
             client_error.error_code = err_code;

include/mtxclient/http/errors.hpp

@@ -19,6 +19,8 @@ struct ClientError
     int status_code;
     //! Parsing response error.
     std::string parse_error;
+
+    const char *error_code_string() const;
 };
 } // namespace http
 } // namespace mtx

lib/structs/errors.cpp

 #include "mtx/errors.hpp"
+#include "mtxclient/http/errors.hpp"
+
+#include <coeurl/errors.hpp>
 
 #include <nlohmann/json.hpp>
 
@@ -108,3 +111,9 @@ from_json(const nlohmann::json &obj, Error &error)
         error.unauthorized = obj.get<user_interactive::Unauthorized>();
 }
 }
+
+const char *
+mtx::http::ClientError::error_code_string() const
+{
+    return coeurl::to_string(static_cast<CURLcode>(error_code));
+}