Add event management features to API, including event cancellation, deletion, registration closure, and workflow balance generation. Introduce new roster management endpoints and enhance participant handling with avoided player preferences. Update database schema and service logic to support these changes.

backend/migrations/008_cancelled_events.sql

@@ -0,0 +1,14 @@
+-- +mixmaker Up
+ALTER TABLE events DROP CONSTRAINT IF EXISTS events_state_check;
+ALTER TABLE events ADD CONSTRAINT events_state_check CHECK (state IN (
+    'RegistrationOpen', 'RegistrationClosed', 'Balancing',
+    'RostersDraft', 'RostersConfirmed', 'Live', 'Completed', 'Cancelled'
+));
+
+-- +mixmaker Down
+UPDATE events SET state = 'Completed' WHERE state = 'Cancelled';
+ALTER TABLE events DROP CONSTRAINT IF EXISTS events_state_check;
+ALTER TABLE events ADD CONSTRAINT events_state_check CHECK (state IN (
+    'RegistrationOpen', 'RegistrationClosed', 'Balancing',
+    'RostersDraft', 'RostersConfirmed', 'Live', 'Completed'
+));