fix: Attachments should not always be deleted with their original document (#1715)

* fix: Attachments should not be deleted when their original document is deleted when referenced elsewhere

* fix: Attachments deleted prematurely when docs are placed in trash

* mock

* restore hook, cascading delete was the issue

server/utils/parseAttachmentIds.js

@@ -0,0 +1,8 @@
+// @flow
+const attachmentRegex = /!\[.*?\]\(\/api\/attachments\.redirect\?id=(?<id>[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12})\)/gi;
+
+export default function parseAttachmentIds(text: any): string[] {
+  return [...text.matchAll(attachmentRegex)].map(
+    (match) => match.groups && match.groups.id
+  );
+}