fix: Fall back to interface language negotiation when content language...
When content language negotiation is not configured as different from interface language negotiation, Drupal stores a "fake" negotiation method called "language-interface" in the content language negotiation config. That means that we must use the interface language negotiation config instead.
I've checked that, in a robust way, taking into account that the dynamic "language-graphql-operation" negotiation method could be present, surely added by the graphql module.
This is the configuration od content language negotiation when content language negotiation is not enabled: $enabledLanguageDetectionMethods = [ "language-interface" => 9, "language-graphql-operation" => -999 ]