AcquirePipelineActivity acquires a lock in the weighted semaphore associated to a particular pipeline.

CleanUpActivity removes the contents that we've created in the TS location.

DownloadActivity downloads the blob into the pipeline processing directory.

PollTransferActivity polls the Transfer Status API repeatedly until processing completes or when an error is considered non permanent.

PopulateMetadataActivity populates the DC identifier in the transfer metadata CSV document.

TransferActivity submits the transfer to Archivematica and returns its ID.