Todoist backend: welcome, and does syncall support Taskwarrior 3.x?

[bluejay-creators]

I'd like to add a Todoist synchronization side (use Taskwarrior as SoT and Todoist as a replica for the phone and other devices), following the "Implement a New Synchronization Service" guide. Two questions before I start:

1. Is a Todoist backend something you'd want upstream, or is there a reason it's been left out so far?
2. Does the current Taskwarrior side work against Taskwarrior 3.x (TaskChampion / SQLite backend), or is it still targeting 2.x? I want to confirm the data layer before building on it.