Goal: 

After the customer clicks on the button to run the conversion, Tasks will send an MQTT message through Cloud Connector to rhcd with a URL from where rhcd downloads the payload - the signed conversion script in a yaml format. Once rhcd successfully downloads the yaml file, it passes it over to the rhc-worker-script to verify the signature and execute the conversion script (HMS-2894). The goal of this ticket is to make sure that Tasks correctly serve the conversion yaml file for download.

Acceptance Criteria:

 * The Tasks API makes the signed conversion script available for download through a unique URL, similarly to how it does it for the pre-conversion analysis script.
 * The signed yaml file containing the conversion script is stored in gitlab (https://gitlab.cee.redhat.com/insights-platform/advisor-backend/-/blob/master/api/advisor/tasks/playbooks/).