As already noted in T259783 this service is not generic, as it should rely on the wiki's content language, and therefore should be moved to SingleEntitySourceServices and MultipleEntitySourceServices or a more appropriate commonplace.
- Service added to SingleEntitySourceServices
- Service added to MultipleEntitySourceServices
- GenericServices LanguageFallbackChainFactory should not be used & should be removed.
This may end up fixing some or all of T259783: LanguageFallbackChain does not end in 'en' for language codes that are not a valid format (currently in the backlog)