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Issue: Channel API endpoints return wrong JSON key "groups" instead of "channels"

Issue: Channel API endpoints return wrong JSON key "groups" instead of "channels": a task in LegoFlow-SWE (Harbor dataset). When calling any of the channel listing endpoints, the JSON response body incorrectly uses the key groups to hold the array of channel objects. It should use channels instead.

The task

When calling any of the channel listing endpoints, the JSON response body incorrectly uses the key **`groups`** to hold the array of channel objects. It should use **`channels`** instead.

Part of Lego-X/LegoFlow-SWE.