Hi Romain,
AFAIK, there is no API for deleting DIPs. I am also very interested in this to clean up my storage service from over a year of testing. In the absence of the API, I am considering going directly into the database and file system to get rid of them. *** any instructions for that would be appreciated! ***
Also, note that the delete_aip endpoint does not delete the AIP, it only submits a request to the SS to delete the AIP. You still need to go into the SS GUI and delete each one. However, it does put them on a single page to approve the deletion...not the cumbersome searching for DIPs that you refer to.
HTH, Don