ALTER TABLE matches
    ADD COLUMN initial_connect_ready_at TIMESTAMPTZ;

-- Existing in-flight matches receive a fresh, fair connection window when
-- this migration is deployed. Future rows are stamped by the transition to
-- ASSIGNMENT_READY, not by match creation or provider allocation.
UPDATE matches
SET initial_connect_ready_at = now()
WHERE state IN ('ASSIGNMENT_READY', 'ASSIGNED', 'CONNECTING');

ALTER TABLE matches
    ADD CONSTRAINT matches_initial_connect_ready_at
    CHECK (state NOT IN ('ASSIGNMENT_READY', 'ASSIGNED', 'CONNECTING') OR initial_connect_ready_at IS NOT NULL) NOT VALID;