[Installer][Client] Back up user data before old uninstallers can delete it

libcockatrice_utility/libcockatrice/utility/user_data_backup.h

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+/**
+ * @file user_data_backup.h
+ * @ingroup Utility
+ * @brief Best-effort safety copies of user data that lives inside the install directory.
+ *
+ * Background: Windows uninstallers shipped in 3.1.0/3.1.1 ran a blanket
+ * "RMDir /r $INSTDIR". For a portable install that deletes $INSTDIR\data
+ * (decks, settings, pictures) along with the payload, and for a normal install
+ * it deletes anything the user pointed into $INSTDIR. The fixed uninstaller
+ * preserves foreign files, but the destructive one is already on disk on
+ * affected machines, so the client keeps a safety copy outside the install
+ * directory before warning the user. Detection of at-risk paths lives in
+ * PathsSettings::pathsInsideDir; this helper only copies.
+ */
+
+#ifndef USER_DATA_BACKUP_H
+#define USER_DATA_BACKUP_H
+
+#include <QString>
+
+namespace UserDataBackup
+{
+
+/**
+ * @brief Recursively copies @p sourceDir into @p destDir, creating it as needed.
+ * @returns true when every file was copied (or there was nothing to copy).
+ */
+bool copyDirectoryRecursively(const QString &sourceDir, const QString &destDir);
+
+/**
+ * @brief Copies an at-risk path (file or directory) to a timestamped folder under @p backupRoot.
+ * @param sourcePath file or directory holding user data (must exist).
+ * @param backupRoot directory OUTSIDE the install tree that will hold timestamped backups.
+ * @param backupLocationOut receives the created backup file or directory on success.
+ * @returns true on success, false when the source is missing or nothing could be copied.
+ */
+bool backupAtRiskPath(const QString &sourcePath, const QString &backupRoot, QString *backupLocationOut = nullptr);
+
+/**
+ * @brief Default backup root guaranteed to live outside the install directory.
+ */
+QString defaultBackupRoot();
+
+} // namespace UserDataBackup
+
+#endif // USER_DATA_BACKUP_H