title: Creating PDF/A-3: Embedded file shall contain valid Params key
body: <p>im trying to create a PDF/A-3 with itextpdf-5.4.5 and itext-pdfa-5.4.5.
  When i set the PdfFileSpecification, i get the following Exception:</p>
  
  <pre><code>com.itextpdf.text.pdf.PdfAConformanceException: Embedded file shall contain valid Params key.
  </code></pre>
  
  <p>This is the part where i create the PdfDictionary:</p>
  
  <pre><code>PdfDictionary params = new PdfDictionary();
  params.put(PdfName.MODDATE, new PdfDate());
  PdfFileSpecification fileSpec = PdfFileSpecification.fileEmbedded(
  writer, "./src/main/resources/com/itextpdf/invoice.xml", "invoice.xml", null, false, "text/xml", params);
  </code></pre>
  
  <p>I found the method where the check happens, but i dont find any solution:</p>
  
  <pre><code>com.itextpdf.text.pdf.internal.PdfA3Checker.checkEmbeddedFile
  
  protected void checkEmbeddedFile(PdfDictionary embeddedFile) {
      PdfDictionary params = getDirectDictionary(embeddedFile.get(PdfName.PARAMS));
      if (params == null) {
          throw new PdfAConformanceException(embeddedFile, MessageLocalization.getComposedMessage("embedded.file.shall.contain.valid.params.key"));
      }
  </code></pre>
  
  <p>Any idea? 
  Thank you in advance!</p>