Narek Aramjan commented on Why do I get a "Required parameter missing or invalid" when trying to create a collection using the API?

Thanks a lot. 

For whoever is interested, here's the working code:

require 'curb'
require 'json'

payload = {
  'custom_collection' => {'title' => 'Test'
  }
}

c = Curl.post('https://<REDACTED>:<REDACTED>@<REDACTED>.myshopify.com/admin/custom_collections.json';, payload.to_json) do |http|
  http.headers['Content-Type'] = 'application/json'
  http.headers['Accept'] = '*/*'
end

puts c.body_str