Rights check on DestroyCorpus

Closes #1104 (closed)

• Clarified the asynchronous deletion in the API description
• Added tests for deletion as a Django admin, deletion of a corpus that does not exist, and deletion without enough rights.

requested review from @babadie

assigned to @erwanrouchet

added 13 commits

• d70e7e6a...a34deff0 - 12 commits from branch master
• d11ded06 - Rights check on DestroyCorpus

Compare with previous version

enabled an automatic merge when the pipeline for d11ded06 succeeds

merged

mentioned in commit e9f5d777