Implement OAuth in middleware for authentication

Currently, header-based authentication is outdated and poses a security risk. Adding OAuth support to the middleware will improve security with modern, token-based authentication.

The issue mentions middleware and replacing header-based auth with OAuth. Look for authentication middleware in the codebase, likely in a middleware or auth module. Research FastAPI OAuth integrations (like OAuth2PasswordBearer) to understand the pattern. The goal is to implement OAuth flow in the existing middleware structure, ensuring tokens are validated.

Scritto dal modello di indicizzazione a partire dal testo della issue.