implement mass cancellation in mediator

This MR also removes the request level cancellation endpoint route as the endpoint apparantly doesn't actually exist... fun times

This is currently deployed to our dev area and has been run locally, on dev, and against production to successfully cancel duplication curation requests.

** The version up on dev is using the 'GET' version of cancellation instead of the correction in this MR as the production service is still using the wrong request type

CAPO_PROFILE=dsoc-<something> mediator -c <space separated list of **capability request ids**>