Design: Act and document how we should pass translation to common components

Summary/TL;DR

We need to unify the behaviour and choose best practices.

Example of diverging practices:

https://gitlab.com/Misakey/app-frontend/blob/develop/src/components/App.js#L52

https://gitlab.com/Misakey/admin-frontend/blob/develop/src/components/App/index.js#L31

NB: For cases of obvious translations, we chose to use withTranslation inside the common component and let the main common.json file hold them + allow override inside external projects

Should we allow a different behaviour?

Detailed description

Steps to do the task

study possibilities:
- generic namespace + override per project
- expecting external components to give translation
discuss block and title if no breaking change