feat: add envelopes (#2025)

This PR is handles the changes required to support envelopes. The new
envelope editor/signing page will be hidden during release.

The core changes here is to migrate the documents and templates model to
a centralized envelopes model.

Even though Documents and Templates are removed, from the user
perspective they will still exist as we remap envelopes to documents and
templates.

packages/ui/components/pdf-viewer/pdf-viewer-konva-lazy.tsx

@@ -0,0 +1,23 @@
+import React, { Suspense, lazy } from 'react';
+
+import { type PDFDocumentProxy } from 'pdfjs-dist';
+
+export type LoadedPDFDocument = PDFDocumentProxy;
+
+export type PDFViewerProps = {
+  className?: string;
+  onDocumentLoad?: () => void;
+  [key: string]: unknown;
+} & Omit<React.HTMLAttributes<HTMLDivElement>, 'onPageClick'>;
+
+const EnvelopePdfViewer = lazy(async () => import('./pdf-viewer-konva'));
+
+export const PDFViewerKonvaLazy = (props: PDFViewerProps) => {
+  return (
+    <Suspense fallback={<div>Loading client component...</div>}>
+      <EnvelopePdfViewer {...props} />
+    </Suspense>
+  );
+};
+
+export default PDFViewerKonvaLazy;