Remove unnecessary failed save form data session handling

[stefanorosanelli]

This PR removes the in-session handling of form data that previously caused server-side errors.

The issue was as follows: when a server-side error occurred while saving an object, the problematic form was displayed after showing the error message. However, upon reloading the object detail page, the form still displayed the erroneous data rather than the current data from the database, as expected. A second reload was required to display the correct data.

Since saving errors are now managed via AJAX, it’s no longer necessary to retain the erroneous data on reload. The in-session handling has therefore been removed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.65%. Comparing base (669fbff) to head (62e2b3c).
Report is 11 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1198      +/-   ##
============================================
- Coverage     99.70%   99.65%   -0.06%     
- Complexity     1310     1326      +16     
============================================
  Files            97       98       +1     
  Lines          5113     5205      +92     
============================================
+ Hits           5098     5187      +89     
- Misses           15       18       +3     

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