bug : replace event.set_results(success=False) with event.fail() in get-cluster-status

[arjun11-malik]

Issue

Fixes Issue #649

Solution

Replaced the improper usage of event.set_results(success=False) with event.fail("...").
Also added a unit test for get-cluster-status action to cover both success and failure scenarios.

Checklist

Checklist

• I have added or updated any relevant documentation.
• I have cleaned any remaining cloud resources from my accounts.

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.37%. Comparing base (e7c1809) to head (7fe7885).
⚠️ Report is 180 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/charms/mysql/v0/mysql.py	75.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #663      +/-   ##
==========================================
- Coverage   66.25%   63.37%   -2.88%     
==========================================
  Files          17       20       +3     
  Lines        3180     4623    +1443     
  Branches      424      759     +335     
==========================================
+ Hits         2107     2930     +823     
- Misses        935     1445     +510     
- Partials      138      248     +110     

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[paulomach]

@arjun11-malik make sure that the output change is not being misinterpreted on the the failing tests

[arjun11-malik]

I’ve double-checked every integration test that invokes get-cluster-status—they only wait for the action to complete and then read out results["status"]. None of them inspect the old success=False payload or rely on its exact shape, so switching to event.fail() on empty status won’t change their behavior.