Added backups of all data, restorable on another computer (#1008)

Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/MindWork AI Studio/Tools/DataBackup/DataBackupReader.cs

@@ -0,0 +1,50 @@
+using System.IO.Compression;
+using System.Text.Json;
+
+using AIStudio.Tools.PluginSystem;
+
+namespace AIStudio.Tools.DataBackup;
+
+/// <summary>
+/// Reads what a backup holds, cf. DataBackupFormat.
+/// </summary>
+/// <remarks>
+/// Open a backup with ZipArchiveMode.Read and read its entries as streams. ZipArchiveMode.Update would
+/// buffer an entry in memory, which ends at 2 GB, and a backup may hold larger files.
+/// </remarks>
+public static class DataBackupReader
+{
+    private static string TB(string fallbackEN) => I18N.I.T(fallbackEN, typeof(DataBackupReader).Namespace, nameof(DataBackupReader));
+
+    /// <summary>
+    /// Reads the manifest of a backup, and checks that this version of AI Studio can use the backup.
+    /// </summary>
+    /// <param name="archive">The backup, opened for reading.</param>
+    /// <param name="token">The cancellation token.</param>
+    /// <returns>The manifest, or why the backup cannot be used.</returns>
+    public static async Task<DataBackupManifestReadResult> ReadManifestAsync(ZipArchive archive, CancellationToken token)
+    {
+        var manifestEntry = archive.GetEntry(DataBackupFormat.MANIFEST_ENTRY_NAME);
+        if (manifestEntry is null)
+            return new(null, TB("This file is no backup of AI Studio, or it was not written completely."));
+
+        DataBackupManifest? manifest;
+        try
+        {
+            await using var manifestStream = manifestEntry.Open();
+            manifest = await JsonSerializer.DeserializeAsync<DataBackupManifest>(manifestStream, DataBackupFormat.JSON_OPTIONS, token);
+        }
+        catch (JsonException)
+        {
+            manifest = null;
+        }
+
+        if (manifest is null)
+            return new(null, TB("The content list of this backup could not be read."));
+
+        if (manifest.FormatVersion > DataBackupFormat.FORMAT_VERSION)
+            return new(null, TB("This backup was made by a newer version of AI Studio. Please update AI Studio first."));
+
+        return new(manifest, string.Empty);
+    }
+}