fix: deletion of subaccounts under managed directories

[lechnerc77]

Purpose

• This PR enhances the deletion logic of subaccounts under managed directories to consider the right level for authorization checks
• Closes [BUG] Deletion of subaccount under directory - authentication error 403 #544

Does this introduce a breaking change?

[ ] Yes
[X] No

Pull Request Type

What kind of change does this Pull Request introduce?

[X] Bugfix
[ ] Feature
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

How to Test

• Test the code via automated test

go test ./...

What to Check

Verify that the following are valid:

• Automated tests are executed successfully

Other Information

n/a

Checklist for reviewer

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• The PR is assigned to the Terraform project and a status is set (typically "in review").
• The PR has the matching labels assigned to it.
• The PR has a milestone assigned to it.
• If the PR closes an issue, the issue is referenced.
• Possible follow-up items are created and linked.

[lechnerc77]

Recreation of test fixtures necessary due to additional call in DELETE to determine parent of subaccount -> Drift detection is okay

[kuntzed]

very nice change