as v3-stable and dev, the spectral line query widget makes a query to the Splatalogue frontend to get line data back. NRAO has been implementing a new AngularJS-based frontend and suggesting us to use the Splatalogue backend for the query instead as it is more straightforward without unnecessary routing.

A doc is prepared for some details.
https://docs.google.com/document/d/1xEZ4_IcyJUo5CermETjOtO96jp4oYC7fJhy7iJlB25I/edit#

Let's try to get this in v4-stable.