feat: store topic title and tags in diffs (#10900)

* feat: store topic title and tags in diffs

allow restoring post diff if tags didn't change

* test: fix tests, fast computer problems

test/posts.js

@@ -425,6 +425,7 @@ describe('Post\'s', () => {
 				cid: cid,
 				title: 'topic to edit',
 				content: 'A post to edit',
+				tags: ['nodebb'],
 			}, (err, data) => {
 				assert.ifError(err);
 				pid = data.postData.pid;