feat(req): Allows setting up Req Plugins on High-level api

[ycastorium]

Description

Allows setting up Req Plugins on High-level api

Type of Change

• Bug fix (non-breaking change fixing an issue)
• New feature (non-breaking change adding functionality)
• Breaking change (fix or feature causing existing functionality to change)
• Documentation update

Breaking Changes

Testing

• Tests pass (mix test)
• Quality checks pass (mix quality)

Checklist

• My code follows the project's style guidelines
• I have updated the documentation accordingly
• I have added tests that prove my fix/feature works
• All new and existing tests pass
• My commits follow conventional commit format
• I have NOT edited CHANGELOG.md (it is auto-generated by git_ops)

Related Issues

Closes #359

[mikehostetler]

Thanks for the contribution! However, I'm going to hold off on merging this for now:

1. Finch streaming not supported - The :req_plugins option only works for non-streaming operations. Streaming uses Finch directly via attach_stream/4, so plugins wouldn't apply there. This creates an inconsistent API surface.

2. Moving away from Req - We're planning to move away from Req in the future, which would make this feature short-lived and potentially a breaking change down the road.

I appreciate the effort here, but given these concerns I don't think this is the right addition at this time.

[ycastorium]

Thanks for the contribution! However, I'm going to hold off on merging this for now:

1. **Finch streaming not supported** - The `:req_plugins` option only works for non-streaming operations. Streaming uses Finch directly via `attach_stream/4`, so plugins wouldn't apply there. This creates an inconsistent API surface.

2. **Moving away from Req** - We're planning to move away from Req in the future, which would make this feature short-lived and potentially a breaking change down the road.

I appreciate the effort here, but given these concerns I don't think this is the right addition at this time.

Aha! Good to know, that you are planning that! Thanks for the input.

[mikehostetler]

Thanks again for the original contribution. I'm adding needs_work to reflect current blocker status before this can land.

This PR is still draft and the current direction concerns from maintainers remain: streaming parity and long-term API direction around Req plugin exposure in high-level APIs.

If you want to continue this, please update scope/proposal to address those points and we can re-evaluate.