Redirect if provider code has the wrong case

When typing an URL including a provider code with the wrong case, the app returns a 404 error.

For example:

• https://db.nomics.world/rosstat returns 404
• https://db.nomics.world/Rosstat returns 404
• https://db.nomics.world/rosstat/wages/AV_WAGES_NB_A returns 404
• https://db.nomics.world/ROSSTAT returns 200
• https://db.nomics.world/ROSSTAT/wages/AV_WAGES_NB_A returns 200

It would be easier for users if the app redirected those 404 URLs to the 200 ones, using 307 HTTP temporary redirection.

This includes the provider page /{provider_code}, the dataset page /{provider_code}/{dataset_code} and the series page /{provider_code}/{dataset_code}/{series_code}.