feat(ExifTool): add capability to overwrite metadata of the PDF generated (#776)

* add new metadata functions to pdf engine interface

* add exiftool module with relevant test cases

* use exiftool to overwrite metadata in libreoffice

* use exiftool to overwrite metadata in chromium

* fix linter issues

* fix more linter issues

* more test cases for better coverage

* remove utils

* minor changes

* remove metadata from pdfoptions

* correct indentation

* read/write metadata one file at a time.

pkg/modules/pdfengines/multi.go

@@ -70,6 +70,52 @@ func (multi *multiPdfEngines) Convert(ctx context.Context, logger *zap.Logger, f
 	return fmt.Errorf("convert PDF to '%+v' with multi PDF engines: %w", formats, err)
 }
 
+func (multi *multiPdfEngines) ReadMetadata(ctx context.Context, logger *zap.Logger, inputPaths string, metadata map[string]interface{}) error {
+	var err error
+	errChan := make(chan error, 1)
+
+	for _, engine := range multi.engines {
+		go func(engine gotenberg.PdfEngine) {
+			errChan <- engine.ReadMetadata(ctx, logger, inputPaths, metadata)
+		}(engine)
+
+		select {
+		case readMetadataErr := <-errChan:
+			errored := multierr.AppendInto(&err, readMetadataErr)
+			if !errored {
+				return nil
+			}
+		case <-ctx.Done():
+			return ctx.Err()
+		}
+	}
+
+	return fmt.Errorf("read PDF metadata with multi PDF engines: %w", err)
+}
+
+func (multi *multiPdfEngines) WriteMetadata(ctx context.Context, logger *zap.Logger, inputPaths string, newMetadata map[string]interface{}) error {
+	var err error
+	errChan := make(chan error, 1)
+
+	for _, engine := range multi.engines {
+		go func(engine gotenberg.PdfEngine) {
+			errChan <- engine.WriteMetadata(ctx, logger, inputPaths, newMetadata)
+		}(engine)
+
+		select {
+		case writeMetadataErr := <-errChan:
+			errored := multierr.AppendInto(&err, writeMetadataErr)
+			if !errored {
+				return nil
+			}
+		case <-ctx.Done():
+			return ctx.Err()
+		}
+	}
+
+	return fmt.Errorf("write PDF metadata with multi PDF engines: %w", err)
+}
+
 // Interface guards.
 var (
 	_ gotenberg.PdfEngine = (*multiPdfEngines)(nil)