Transfer cancellation requests report 'failed' status, not 'canceled', and records are prematurely purged.

[jeff-cohere]

I recently cancelled a large transfer using the DTS cancellation feature, and it worked insofar as the transfer was halted. However, the status was marked as a failure, not a cancellation, and the transfer record was purged, making it impossible for anyone to check on its status subsequently. Here's what the logs say:

{"time":"2025-08-20T18:22:58.612505848Z","level":"INFO","msg":"Task 3a1a85c3-3358-4381-ac1f-7803d2179ef6: received cancellation request"}
2025-08-20T18:22:58.612689473Z {"time":"2025-08-20T18:22:58.61256724Z","level":"DEBUG","msg":"POST: https://transfer.api.globusonline.org/v0.10/task/b27353cc-7def-11f0-99d6-022f00a2b23f/cancel"}
{"time":"2025-08-20T18:23:29.294429253Z","level":"DEBUG","msg":"GET: https://transfer.api.globusonline.org/v0.10/task/b27353cc-7def-11f0-99d6-022f00a2b23f"}
{"time":"2025-08-20T18:23:29.442228164Z","level":"INFO","msg":"Task 3a1a85c3-3358-4381-ac1f-7803d2179ef6: failed"}
{"time":"2025-08-20T18:23:29.695663205Z","level":"DEBUG","msg":"Task 3a1a85c3-3358-4381-ac1f-7803d2179ef6: purging transfer record"}

Seems like it won't be much work to track this down.

[jeff-cohere]

Revisiting the code, I see that while the status code reflects a "failed" transfer, the message conveys that a transfer was canceled at the request of a user. Since I haven't identified a programmatic need to distinguish between "failure" and "cancellation", I think this is fine for now. But the transfer record purge is still an issue.