feat: add product variant management functionality

- Implemented CreateProductVariantDto and UpdateProductVariantDto for product variant data transfer.
- Developed ProductVariantsController to handle CRUD operations for product variants.
- Created ProductVariantsService to interact with the database using Prisma.
- Added ProductVariantsModule to encapsulate the product variant feature.
- Included response mapping for consistent API responses.

prisma/seed.ts

@@ -0,0 +1,22 @@
+import { prisma } from '../src/lib/prisma'
+
+async function main() {
+  console.log('first')
+
+  await prisma.role.upsert({
+    where: { id: 0, name: 'Admin' },
+    update: {},
+    create: {
+      name: 'Admin',
+    },
+  })
+}
+main()
+  .then(async () => {
+    await prisma.$disconnect()
+  })
+  .catch(async e => {
+    console.error(e)
+    await prisma.$disconnect()
+    process.exit(1)
+  })