Bypass user checks for anonymously posted posts and topics

[cathyxfeiyang]

Update topics/user.js and posts/user.js to modify ownership check logic to handle anonymous posts and topics

Effort: medium Dependencies: https://github.com/CMU-313/spring24-nodebb-apple/issues/30

Acceptance criteria:

• unit testing validating that anonymous posts can pass permission checks, with at least 90% coverage for added lines
• manual testing that posts and topics can be successfully created manually
• manual testing that anonymously made posts are not associated with users