fix: multi threading compliance

[Quentinchampenois]

Description

The current implementation isn't thread-safe. On multi-threaded decidim application users may find inconsistencies on the modified translations.
I was able to reproduce a race condition on the proposals index view. Modifying the translation of decidim.proposals.application_helper.filter_state_values.evaluating and using a scraper inspecting the label text with 4 threads and 100 requests per thread.

Related to

#107

Testing

• Modify a translation
• Activate cache
• Enable multi-threading on application
• Make multiple concurrent requests on application

Additional information

I tested with different environments :

• single thread puma
• 5 threads puma
• 4 workers and 5 threads per worker puma

I am not sure the current PR is fully thread-safe but I notice a reduction of inconsistencies.

I can share the application used with different configuration, and also the scraper used if wanted

[BigSnicker]

Is there a timeline for this getting pulled into master?

[Quentinchampenois]

I share with you a feedback about this solution,
I notice a reduction of inconsistencies but I don't think this is completely fixed with this solution