fix(webdav): skip Nextcloud trashbin for backup cleanup

[arpitagarwal1301]

Closes #1037

Summary

• Send X-NC-Skip-Trashbin: true with WebDAV cleanup DELETE requests.
• Cover both individual and whole-backup deletion paths with a focused unit test.

Validation

• :core:testDebugUnitTest --tests '*WebDavBackendTest*'
• :core:check :core:assemble :core:ktlintCheck

[grote]

Thanks for the contribution. Did you actually test this against a supporting Nextcloud server?

[grote]

This seems to mix the integration tests with a unit test. Best to make a new test class for it.

[arpitagarwal1301]

I did not test this against a live Nextcloud instance because I do not currently have a supporting server available. I verified both cleanup paths pass X-NC-Skip-Trashbin: true to dav4jvm with the focused unit test, and I split that test into WebDavBackendUnitTest as requested. The existing credential-dependent WebDAV integration tests remain unchanged and skipped locally because the NEXTCLOUD_* variables are unavailable. If live-server verification is required, I will need a private test instance or a locally provisioned Nextcloud environment.

[tbrandirali]

@arpitagarwal1301 thank you so much for working on the feature I requested! I don't really have the time to build and test this branch myself right now, but I could probably spin up a test instance of Nextcloud for you to test it against. It might take me a few days to find the time, but if you don't have another option I'd be happy to help out.

[arpitagarwal1301]

Thank you—that would be very helpful. Please don’t post credentials here. If you can prepare a temporary Nextcloud 31+ instance with a dedicated, empty test account, let me know and we can agree on a private handoff method. I’ll use it only to test this branch and confirm when the account can be deleted.

[grote]

@tbrandirali this would be very appreciated! I'd prefer merging this only after it has been actually verified in practice against a real server.

[tbrandirali]

After a bit more thought I think I'd rather run the test myself, spinning up a Nextcloud instance for someone else would be more work. @grote would running the integration tests against my live Nextcloud instance on a fresh account be sufficient for you, or would you require a full emulator backup test?

The integration tests do run DELETEs, so I can check that there are no leftovers in the trash bin after running them.

[grote]

@tbrandirali since seedvault needs to be a system app, getting a dev setup isn't trivial. I think creating a test account on your nextcloud instance should be way easier, but as you prefer. ideally, you run the integration tests against the server and also do a manual test.

[tbrandirali]

@arpitagarwal1301 I spun up a test instance for this and emailed you about exchanging credentials. @grote let me know if you would also want a test account.