Add adyen_sessions.authorisation_webhook_timestamp and make adyen_session_id unique (#403)

migrations/000.482.sql

@@ -0,0 +1,5 @@
+-- Add column to register when authorisation webhook was received
+ALTER TABLE adyen_sessions ADD COLUMN IF NOT EXISTS authorisation_webhook_timestamp TIMESTAMP WITH TIME ZONE;
+
+-- Make adyen_session_id unique
+CREATE UNIQUE INDEX ON adyen_sessions(adyen_session_id);