This PR introduces a new `Auth Storage` abstraction layer that takes care of read, write, and load of auth tokens based on the AuthCredentialsStoreMode. It is similar to how we handle MCP client oauth [here](https://github.com/openai/codex/blob/main/codex-rs/rmcp-client/src/oauth.rs). Instead of reading and writing directly from disk for auth tokens, Codex CLI workflows now should instead use this auth storage using the public helper functions. This PR is just a refactor of the current code so the behavior stays the same. We will add support for keyring and hybrid mode in follow-up PRs. I have read the CLA Document and I hereby sign the CLA
ChatGPT
This crate pertains to first party ChatGPT APIs and products such as Codex agent.
This crate should be primarily built and maintained by OpenAI employees. Please reach out to a maintainer before making an external contribution.