NOISSUE refactor *Download into more, smaller pieces

* Download is now Download.
* Download uses Sink subclasses to process various events.
* Validators can be used to further customize the Sink behaviour.

api/logic/net/FileSink.h

@@ -0,0 +1,27 @@
+#pragma once
+#include "Sink.h"
+#include <QSaveFile>
+
+namespace Net {
+class FileSink : public Sink
+{
+public: /* con/des */
+	FileSink(QString filename);
+	virtual ~FileSink();
+
+public: /* methods */
+	JobStatus init(QNetworkRequest & request) override;
+	JobStatus write(QByteArray & data) override;
+	JobStatus abort() override;
+	JobStatus finalize(QNetworkReply & reply) override;
+
+protected: /* methods */
+	virtual JobStatus initCache(QNetworkRequest &);
+	virtual JobStatus finalizeCache(QNetworkReply &reply);
+
+protected: /* data */
+	QString m_filename;
+	bool wroteAnyData = false;
+	std::unique_ptr<QSaveFile> m_output_file;
+};
+}