D7: Add multilingual support

Problem/Motivation

Currently, only the 1.x version supports multilingual sites. Given the D7 EOL is January 2025, we may not want to add this feature, but adding it for now as postponed in case there is someone who needs this and we decide to move forward with it.

Steps to reproduce

Proposed resolution

Add multilingual support for nodes, terms, redirects and sitemaps.

Remaining tasks

• Decide if we should add this and if so...
• Update code
• Review and test
• Commit :)

User interface changes

TBD if languages would be configurable like in 1.x version.

API changes

Data model changes