Add fk constraint on logs

db/migrations/1516050071_add_log_fk_constraint.down.sql

@@ -0,0 +1,9 @@
+BEGIN;
+
+ALTER TABLE logs
+  DROP CONSTRAINT receipts_fk;
+
+ALTER TABLE logs
+  DROP COLUMN receipt_id;
+
+COMMIT;

db/migrations/1516050071_add_log_fk_constraint.up.sql

@@ -0,0 +1,12 @@
+BEGIN;
+
+ALTER TABLE logs
+  ADD COLUMN receipt_id INT;
+
+ALTER TABLE logs
+  ADD CONSTRAINT receipts_fk
+FOREIGN KEY (receipt_id)
+REFERENCES receipts (id)
+ON DELETE CASCADE;
+
+COMMIT;