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.

src/main.ts

@@ -1,7 +1,8 @@
-import { VersioningType } from '@nestjs/common'
+import { ValidationPipe, VersioningType } from '@nestjs/common'
 import { NestFactory } from '@nestjs/core'
 import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger'
 import { AppModule } from './app.module'
+import { PrismaExceptionFilter } from './common/filters/prisma-exception.filter'
 import { LoggingInterceptor } from './common/interceptors/logging.interceptor'
 import { ResponseMappingInterceptor } from './common/interceptors/response-mapping.interceptor'
 
@@ -43,6 +44,12 @@ async function bootstrap() {
   // Register global logging and response mapping interceptors
   app.useGlobalInterceptors(new LoggingInterceptor(), new ResponseMappingInterceptor())
 
+  // Enable request validation and transformation globally
+  app.useGlobalPipes(new ValidationPipe({ whitelist: true, transform: true }))
+
+  // Register global exception filter to map Prisma and validation errors to proper HTTP codes
+  app.useGlobalFilters(new PrismaExceptionFilter())
+
   await app.listen(process.env.PORT ?? 3000)
 }
 bootstrap()