Preview mentions (#5571)

Co-authored-by: Tom Moor <tom.moor@gmail.com>

server/presenters/unfurls/mention.ts

@@ -0,0 +1,23 @@
+import { Unfurl, UnfurlType } from "@shared/types";
+import { Document, User } from "@server/models";
+import { presentLastOnlineInfoFor, presentLastViewedInfoFor } from "./common";
+
+function presentMention(
+  user: User,
+  document: Document
+): Unfurl<UnfurlType.Mention> {
+  return {
+    type: UnfurlType.Mention,
+    title: user.name,
+    description: `${presentLastOnlineInfoFor(
+      user
+    )} • ${presentLastViewedInfoFor(user, document)}`,
+    thumbnailUrl: user.avatarUrl,
+    meta: {
+      id: user.id,
+      color: user.color,
+    },
+  };
+}
+
+export default presentMention;