bugfix: sanitize gh_token & avoid panic

[acidghost]

Fixes #1021.

✨ Copilot summary

This pull request refactors the handling of GitHub API tokens and clients across the codebase, replacing the previous token-based approach with a new `GitHubToken` struct and updating related logic to improve encapsulation and error handling. Additionally, it modifies the `AuditState` structure to directly store an optional GitHub client instead of a token, simplifying client initialization and usage.

Refactoring GitHub API Token Handling:

• Introduced the GitHubToken struct in crates/zizmor/src/github_api.rs to encapsulate and validate GitHub tokens. Added methods for sanitizing token input and converting tokens to header values.
• Updated the Client::new method to accept a GitHubToken instance instead of a raw string, improving error handling during header creation. (F889a5b4L89R128)

Changes to AuditState Structure:

• Replaced gh_token and cache_dir fields in AuditState with an optional gh_client field, directly storing a pre-configured GitHub client. Updated the AuditState::new method to initialize the client based on the presence of a token. [1] [2]

Updates to Audit Implementations:

• Refactored audit implementations (ImpostorCommit, KnownVulnerableActions, RefConfusion, StaleActionRefs) to use the new gh_client field directly, simplifying error handling and client initialization logic. [1] [2] [3] [4]

Test Updates:

• Updated tests across multiple files to reflect the removal of gh_token and the addition of gh_client. Added new tests for GitHubToken validation and sanitization. [1] [2] [3] [4] [5]

Other Changes:

• Updated command-line argument parsing in crates/zizmor/src/main.rs to use GitHubToken::from_clap for validating tokens.

[woodruffw]

Flagging: maybe not worth fixing with this PR, but it seems non-ideal that we now have to re-check the error state on GitHubClient on each audit initialization. Maybe we should create a single Option<GitHubClient> on the audit state instead.

(Feel free to look into that if you feel like it; otherwise that can wait until another refactor 🙂)

[acidghost]

I tried to play around with lifetimes to avoid cloning the Client and keep a reference in the Audit implementations, but I've not been using much Rust in the past year and it was starting to get like a bigger rabbit hole than I can dig through at the moment 😄

[woodruffw]

No worries at all, thanks for poking at it!

[woodruffw]

LGTM -- I wish we didn't have to clone the GitHub client in so many places, but it's a pretty small cost given that we reuse each audit many times.

[woodruffw]

Thanks @acidghost!