Investigate undocumented CrowdFlower API request to enable internal and external channels

[marfox]

The action has to be done manually via the UI, no API implementation/documentation seems available. Current UI procedure: job > settings > show advanced settings > contributors tab > internal/external contributors switch

[marfox]

This seems to be bound to the launch of a job:

curl -X POST -d "channels[0]=on_demand&channels[1]=cf_internal&debit[units_count]={100}" https://api.crowdflower.com/v1/jobs/{job_id}/orders.json?key={api_key}