Optimize Post Model Schema

[NeyuD96155]

Problem:
The current Post model schema includes references and array fields that are not indexed. This could potentially slow down query performance as the dataset grows.

Proposed Change:

• Add indexes to author and potentially tags fields to improve query performance.
• Evaluate the necessity of indexing status based on query patterns in the application.

Expected Outcome:
Improved performance for queries involving the Post model, especially when filtering by author, tags, or status.