udisks doesn't recognize volumes with multiple encryption as unlocked

VeraCrypt supports using multiple encryption (see https://www.veracrypt.fr/en/Cascades.html). When unlocking a volume with multiple encryption, the CryptoBackingDevice property is not set, which seems to be the reason for the volume not being recognized as unlocked (neither in GNOME Disks nor in Unlock VeraCrypt Volumes).

As a result, the timeout for waiting for cleartext object after unlocking is always exceeded (the cleartext object never appears), therefore users using volumes with multiple encryption are also affected by #15733 (closed) (and consequently #15757 (closed), if they find the cleartext volume in GNOME Disks and try to unlock it).

Upstream merge request: https://github.com/storaged-project/udisks/pull/582 (merged)

Feature Branch: feature/14481-TCRYPT-support-beta

Related issues

Related to #15733 (closed)

Original created by @segfault on 15967 (Redmine)

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