collab: Add `POST /users/:id/update_plan` endpoint (#34953)
This PR adds a new `POST /users/:id/update_plan` endpoint to Collab to
allow Cloud to push down plan updates to users.
Release Notes:
- N/A
14171e0721Marshall Bowers committed on 7/23/2025, 2:30:08 PM· committed by GitHubparent326ab5f