feat: send personal player notifications

src/GmRelay.Bot/Migrations/V007__add_session_notification_mode.sql

@@ -0,0 +1,8 @@
+ALTER TABLE sessions
+    ADD COLUMN notification_mode VARCHAR(50) NOT NULL DEFAULT 'GroupAndDirect'
+        CHECK (notification_mode IN ('GroupAndDirect', 'GroupOnly')),
+    ADD COLUMN one_hour_reminder_processed_at TIMESTAMPTZ;
+
+CREATE INDEX ix_sessions_one_hour_reminders ON sessions (scheduled_at)
+    WHERE status IN ('Confirmed', 'ConfirmationSent')
+      AND one_hour_reminder_processed_at IS NULL;