Handle missing disk versions

[artonge]

This PR is a palliative upon groupfolders failing to move versions correctly when a file is moved across storage.

1. Delete versions folder when we detect that the original file in the group folder is not there anymore.(GroupVersionsExpireManager.php)
2. Create the version folder before reading it (VersionsBackend.php).
3. Delete version entity in the DB if the disk counterpart does not exist (VersionsBackend.php).

Fix #2559

[artonge]

/backport to stable28

[artonge]

/backport to stable27

[backportbot-nextcloud]

The backport to stable27 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable27
git pull origin stable27

# Create the new backport branch
git checkout -b fix/foo-stable27

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts. Resolve them.
git cherry-pick abc123

# Push the cherry pick commit to the remote repository and open a pull request
git push origin fix/foo-stable27

Error: Unknown error

More info at https://docs.nextcloud.com/server/latest/developer_manual/getting_started/development_process.html#manual-backport

[EDVB-Paulick]

When is this patch available in 28? We really need it.

Cheers

[artonge]

When is this patch available in 28? We really need it.

If this is important to you, please get a subscription at Nextcloud :).

[EDVB-Paulick]

When is this patch available in 28? We really need it.

If this is important to you, please get a subscription at Nextcloud :).

You are right, we are working on this issue internally ... ;-)