Correctif : exclut les dossiers en brouillon de la recherche (etq instructeur)

[E-L-T]

Lorsqu'un instructeur faisait une recherche par id d'un dossier encore en brouillon (donc sans groupe instructeurs) on avait une erreur 500.

cf https://demarches-simplifiees.sentry.io/issues/4275606696/?project=1429550&query=is%3Aunresolved&referrer=issue-stream&stream_index=2

[what-the-diff]

PR Summary

• Enhanced Search Functionality in 'recherche_controller.rb'
  This PR adds a new condition in the search controller, enhancing the search function to identify and ignore any unprocessed and incomplete files, known as 'drafts'. This means that search results will only display completed files, streamlining the search process for users.

• User-Specified Access Boundaries
  To further refine the search function and enhance privacy features, another condition was added to the search controller. The update ensures that only cases assigned to a user, or 'instructor', will appear in their search results. If a case falls outside of an instructor's domain, the system will not include it in the provided results, reinforcing security measures.

• Extended Test Coverage
  This PR introduces a new test scenario under 'recherche_controller_spec.rb' to ensure the newly implemented conditions are effective. This specific test verifies that when unassigned drafts are part of the search, these preliminary files aren't included in the search results. Consequently, this bolsters confidence in the system's ability to only fetch relevant and completed files.