Create proper canonical structure

[txau]

Because we have a lot of duplication of content, we should add proper canonicals to avoid penalization in SEO. When we have a default language (eg. EN) and we are in the English language, we have two URLs with duplicated content in library and entities. Eg.

https://host.dom/library/something
https://host.dom/en/library/something

and

https://host.dom/entity/something
https://host.dom/en/entity/something

This may also be the case for certain URLs inside entities:

https://host.dom/entity/something/references
https://host.dom/entity/something