Fix schema

postgres/schema/0007_category-groups.sql

@@ -0,0 +1,9 @@
+-- +goose Up
+CREATE TABLE category_groups (
+    id uuid DEFAULT uuid_generate_v4() PRIMARY KEY,
+    budget_id uuid NOT NULL REFERENCES budgets (id) ON DELETE CASCADE,
+    name varchar(50) NOT NULL
+);
+
+-- +goose Down
+DROP TABLE category_groups;