line multi authors

static/js/authorship.js

@@ -92,6 +92,10 @@ export function replaceAuthorshipOwner(model, matcher, replacement, contentLengt
 }
 
 
+export function authorshipOwners(model) {
+  return [...new Set((model?.spans || []).map(span => span.owner).filter(Boolean))];
+}
+
 export function lineAuthors(content, model) {
   const starts = [0];
   for (let i = 0; i < content.length; i++) if (content.charCodeAt(i) === 10) starts.push(i + 1);