feat: assistant role (#1588)

Introduces the ability for users with the **Assistant** role to prefill
fields on behalf of other signers. Assistants can fill in various field
types such as text, checkboxes, dates, and more, streamlining the
document preparation process before it reaches the final signers.

apps/remix/app/components/embed/embed-document-waiting-for-turn.tsx

@@ -0,0 +1,46 @@
+import { useEffect, useState } from 'react';
+
+import { Trans } from '@lingui/react/macro';
+
+export const EmbedDocumentWaitingForTurn = () => {
+  const [hasPostedMessage, setHasPostedMessage] = useState(false);
+
+  useEffect(() => {
+    if (window.parent && !hasPostedMessage) {
+      window.parent.postMessage(
+        {
+          action: 'document-waiting-for-turn',
+          data: null,
+        },
+        '*',
+      );
+    }
+
+    setHasPostedMessage(true);
+  }, [hasPostedMessage]);
+
+  if (!hasPostedMessage) {
+    return null;
+  }
+
+  return (
+    <div className="relative mx-auto flex min-h-[100dvh] max-w-screen-lg flex-col items-center justify-center p-6">
+      <h3 className="text-foreground text-center text-2xl font-bold">
+        <Trans>Waiting for Your Turn</Trans>
+      </h3>
+
+      <div className="mt-8 max-w-[50ch] text-center">
+        <p className="text-muted-foreground text-sm">
+          <Trans>
+            It's currently not your turn to sign. Please check back soon as this document should be
+            available for you to sign shortly.
+          </Trans>
+        </p>
+
+        <p className="text-muted-foreground mt-4 text-sm">
+          <Trans>Please check with the parent application for more information.</Trans>
+        </p>
+      </div>
+    </div>
+  );
+};