add README.md

feat: implement advanced search with multiple criteria using MongoDB @Query

feat: implement custom @Query for case-insensitive title search in posts

feat: implement title search endpoint using query methods

feat: add CommentDTO, associate comments with posts, and update database seed

feat: create PostService and implement findById endpoint

feat: add endpoint to fetch posts by user id

feat: add posts reference to User with lazy DBRef mapping

refactor(post): decouple Post from User by introducing AuthorDTO

feat: add Post entity, repository, and database seed data with author association

feat: implement user update with DTO mapping and selective field update

feat: implement user deletion with existence validation and 404 handling

feat: implement user creation endpoint with DTO mapping and location header

feat: implement findById endpoint and standardized error response for non-existent resources

feat: use DTO pattern to return users