Set minimum priority for manual jobs

[alejandrocobo]

Describe the problem to be solved

As for now, when I run some jobs manually (ie. to transcode finished live-streams), the jobs don't have a priority number. So when a user uploads a new video, the uploaded video transcoding won't start until all the manually added jobs are finished.

Describe the solution you would like

I don't know if this is the desired behavior but I think it would be better to assign a very low priority to manual jobs so the public queue doesn't get stuck for a long time.

Thanks.