Update Signature App.vue to use a converted pdf

Introduced a new helper ts function to download documents as PDFs and integrated with the existing workflow. Enhanced `PDFSignatureZoneAvailable` to implement `LocaleAwareInterface` for better locale management and added PDF conversion handling for non-PDF documents. Updated App.vue to use the new PDF download method.

src/Bundle/ChillDocStoreBundle/Resources/public/vuejs/StoredObjectButton/helpers.ts

@@ -197,6 +197,32 @@ async function download_and_decrypt_doc(storedObject: StoredObject, atVersion: n
    }
 }
 
+/**
+ * Fetch the stored object as a pdf.
+ *
+ * If the document is already in a pdf on the server side, the document is retrieved "as is" from the usual
+ * storage.
+ */
+async function download_doc_as_pdf(storedObject: StoredObject): Promise<Blob>
+{
+    if (null === storedObject.currentVersion) {
+        throw new Error("the stored object does not count any version");
+    }
+
+    if (storedObject.currentVersion?.type === 'application/pdf') {
+        return download_and_decrypt_doc(storedObject, storedObject.currentVersion);
+    }
+
+    const convertLink = build_convert_link(storedObject.uuid);
+    const response = await fetch(convertLink);
+
+    if (!response.ok) {
+        throw new Error("Could not convert the document: " + response.status);
+    }
+
+    return response.blob();
+}
+
 async function is_object_ready(storedObject: StoredObject): Promise<StoredObjectStatusChange>
 {
     const new_status_response = await window
@@ -214,6 +240,7 @@ export {
   build_wopi_editor_link,
   download_and_decrypt_doc,
   download_doc,
+  download_doc_as_pdf,
   is_extension_editable,
   is_extension_viewable,
   is_object_ready,