Returns your company's active lead stages in pipeline order. Each stage reports its name, color,
icon and system_state (the outcome it maps to: open, won, lost or inactive), and the
parent_id and parent_name of the stage group it sits under, so you can render the pipeline as
grouped columns. Use these IDs with PATCH /leads/{id}/move_to_stage and the lead_stage_ids[]
filter on GET /leads.

Any authenticated user can call this endpoint.