Week 4 in-class: REST layers

Synced from si-679-f-26-week-04-nyt-jessicadonoho/. These are copies; the original folder is untouched.

• FIXES.md
• package.json
• README.md
• tsconfig.json
• vitest.config.ts
• sampleData/customers-with-ids.json
• sampleData/products.json
• src/__tests__/products.test.ts
• src/app.ts
• src/controllers/product-controllers.ts
• src/db/db.ts
• src/index.ts
• src/middleware/error-handler.ts
• src/models/products.ts
• src/routes/product-routes.ts
• src/services/product-service.ts