[stable31]: fix(auth): Fix invalid unique constraint violation catch

[CarlSchwan]

Summary

UniqueConstraintViolationException is no longer throw but instead a OCP\DB\Exception is.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[Antreesy]

Looks aligned with another PRs)

[kesselb]

Thank you

[CarlSchwan]

/backport to stable30

[backportbot]

The backport to stable30 failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout stable30
git pull origin stable30

# Create the new backport branch
git checkout -b backport/55123/stable30

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick 47ce9c4c

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/55123/stable30

Error: Failed to push branch backport/55123/stable30: remote: Invalid username or token. Password authentication is not supported for Git operations.
fatal: Authentication failed for 'https://github.com/nextcloud/server.git/'

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Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.