[QoS Booking] Test definitions: missing error scenarios, duplicate tag, stale serviceArea note #166

Problem description

Gaps in the test definitions of qos-booking 0.2.0-rc.2:

1. No scenarios exist for 422 EVENT_NOTIFICATIONS_NOT_SUPPORTED, 400 INVALID_CREDENTIAL and 429 TOO_MANY_REQUESTS, although all three are declared in the API definition.
2. The tag @qos_booking_createBooking_400.10_... is used twice (qos-booking-createBooking.feature L297 and L363).
3. The note at L57 says a serviceArea equality rule agreed in the CQM meeting of 2026-02-06 still awaits an API spec update. Either the update is missing or the note is outdated.

Expected action

Add the missing scenarios, make the tags unique, and resolve or remove the note.

Additional context

Found in the review of release r2.2 snapshot #160.