Search by language

This MR allows the consumers of the API to filter the results of the search by the language.

How to test:

First, you will need to have a folder in which to test your indexation results.

For better indexation results, checkout the commit f9a45ed098b54c0ec9c2468342f873aa726e8f81 on the user documentation project. After that, you can run the following command on the root of the user documentation project:

docker run --rm --volume="$PWD/htdocs:/srv/jekyll" -p 4000:4000 -p 35729:35729 -it jekyll/jekyll:4.2.0 jekyll build

After that, follow the installation instructions and the development instructions at here.

Now, with the flask running, go to http://localhost:5000/en/search/faq and http://localhost:5000/fr/search/faq . Assert that the results are based on the selected language.