feat: add flowing templates and PDF import pipeline

LehrerApp.Templating/TemplatePackage.cs

@@ -8,7 +8,7 @@ public static class TemplatePackage
     public const string Extension = ".lavorlage";
 
     public static void Create(string outputPath, TemplateManifest manifest, string layoutSource,
-        IReadOnlyDictionary<string, byte[]> assets)
+        IReadOnlyDictionary<string, byte[]> assets, string? continuationLayoutSource = null)
     {
         if (!TemplateLoader.IsSafeRelativePath(manifest.MetadataFile))
             throw new InvalidDataException("metadataFile enthält einen unsicheren Pfad.");
@@ -17,6 +17,14 @@ public static class TemplatePackage
             throw new InvalidDataException("metadataFile und layoutFile dürfen nicht identisch sein.");
         var reservedPaths = new HashSet<string>(StringComparer.OrdinalIgnoreCase)
         { "manifest.json", TemplateLoader.Normalize(manifest.LayoutFile), TemplateLoader.Normalize(manifest.MetadataFile) };
+        if (manifest.ContinuationLayoutFile is { } continuationPath)
+        {
+            if (!TemplateLoader.IsSafeRelativePath(continuationPath))
+                throw new InvalidDataException("continuationLayoutFile enthält einen unsicheren Pfad.");
+            reservedPaths.Add(TemplateLoader.Normalize(continuationPath));
+            if (continuationLayoutSource is null)
+                throw new InvalidDataException("Das Folgeseiten-Layout fehlt.");
+        }
         if (!string.Equals(Path.GetExtension(outputPath), Extension, StringComparison.OrdinalIgnoreCase))
             outputPath += Extension;
         var directory = Path.GetDirectoryName(outputPath);
@@ -28,6 +36,8 @@ public static class TemplatePackage
             {
                 WriteText(archive, "manifest.json", JsonSerializer.Serialize(manifest, TemplateLoader.JsonOptions));
                 WriteText(archive, manifest.LayoutFile, layoutSource);
+                if (manifest.ContinuationLayoutFile is { } continuationFile)
+                    WriteText(archive, continuationFile, continuationLayoutSource!);
                 WriteText(archive, manifest.MetadataFile, TemplateMetadataText.Serialize(manifest.Metadata));
                 foreach (var asset in assets)
                 {