A guest was provisioned with only its detected time zone; its PreferredLanguage
fell to the 'en' column default. The client already sends its locale in the guest
login (GuestLoginRequest.locale), but the gateway dropped it and ProvisionGuest
took no language — so a Russian user's brand-new native guest got English
language-dependent server content (the ad banner, bot messages) until the client's
later language reconcile. Read the locale in the gateway guest handler, thread it
through GuestAuth -> ProvisionGuest, and seed PreferredLanguage from it (validated;
an unsupported/absent value keeps the 'en' default). Wire field already present —
no schema change.
Ilia Denisov
f8aeec8008