Handle errors while deleting and renaming files

[DeepDiver1975]

Description

Delete and rename operations did not handle error conditions at all before this PR.
While it is UX-wise far from good - this is better then nothing.

The whole error handling flow as well as the user confirmation flow is under review at the moment.

As say: better then nothing

How Has This Been Tested?

• Lock a file using webdav locks (cadaver or manual insert into database)
• try to delete or rename
• see error notification

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised:

Open tasks:

• ...