Add lint, build, and test commands to justfile, add fmt and clippy to CI workflow

[austin-denoble]

Problem

@haruska had some good feedback around adding explicit build, test, and lint commands to the justfile in the repo. Currently there are only commands for dealing with code generation which is a little confusing.

Additionally, we haven't run cargo fmt and cargo clippy on the codebase yet, and have nothing enforcing its use.

Solution

• Refactorjustfile: move all code generation under gen-* commands, add build, test, lint, and update commands to the file.
• Update ci.yaml workflow to support both fmt and clippy. Reject if running either leads to issues.
• Code changes for fmt and clippy.

Note: At the moment I've added #![allow(clippy::enum_variant_names)] and #![allow(clippy::empty_docs)] to the src/openapi/mod.rs file. There were some clippy issues in the generated code, and since we still need to refactor the entire generation flow in this repo, I just stuck the allow tags on top for now.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• Infrastructure change (CI configs, etc)
• Non-code change (docs, etc)
• None of the above: (explain here)

Test Plan

Make sure CI passes.

[haruska]

Good improvement. Might also want to clean up the check-annotations on the build.

[haruska]

i'd put this under a gen-* prefix as well

[haruska]

might want to add a comment for consistency.