Bugfix: Domain save issue

[ziyacivan]

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Checklist

• I have double checked that there are no unrelated changes in this pull request (old patches, accidental config files, etc.)
• [] I have created at least one test case for the changes I have made
• I have updated the documentation for the changes I have made
• I have added my changes to the CHANGELOG.md

Pull Request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

Related issue(s)

Other Information

I observed an issue within an edge-case scenario. After executing the code block below:

instance.delete_tenant()

I noticed that the domain_url field on the instance remained unchanged. The changes only became visible after I explicitly called instance.save(). Due to this inconsistency, I have created this pull request.

[Dresdn]

@ziyacivan I see there are changes to some tests, but they look like formatting changes only. I don't know if you added or updated a test that showcases the bug and forgot to commit, but I wanted to check before adding one myself. Would be great to have a test for this edge case.