feat(runtime): generate environment configuration layer

[dev-queiroz]

Summary

Generate environment configuration module with Zod validation and typed access to environment variables.

Motivation

Real backends need environment-based configuration (database URL, port, secrets). Currently developers must write this manually. This feature generates a production-ready ConfigService with runtime validation using Zod.

Scope

In Scope

• .env.example file with all required variables
• src/config/ module with ConfigService
• Zod schema validation at startup
• Support for NODE_ENV (development/production/test)
• DATABASE_URL validation
• Port configuration (default 3000)
• JWT_SECRET validation (if auth enabled)
• Clear error messages if required vars missing

Out of Scope

• Vault/secret management integration
• Environment variable encryption
• Configuration hot-reload

Acceptance Criteria

• .env.example generated with all variables
• src/config/config.service.ts generated
• ConfigService is @Injectable()
• Zod schema validates at app startup
• Fails startup if required var missing
• NODE_ENV supports development/production/test
• DATABASE_URL validated as URL format
• PORT can be configured via env (default 3000)
• JWT_SECRET validated if auth feature enabled
• Error messages are clear and actionable
• ConfigService exported from app.module

Files to Create/Modify

• packages/generators/src/nest/templates/config.service.template.ts (NEW)
• packages/generators/src/nest/templates/.env.example (NEW)
• packages/generators/src/nest/generator.ts (MODIFY)
• tests/nest-config.test.mjs (NEW)

Example Output

// src/config/config.service.ts
import { z } from 'zod';

const EnvSchema = z.object({
  NODE_ENV: z.enum(['development', 'production', 'test']).default('development'),
  PORT: z.coerce.number().default(3000),
  DATABASE_URL: z.string().url(),
  JWT_SECRET: z.string().min(32),
});

@Injectable()
export class ConfigService {
  private config: z.infer<typeof EnvSchema>;

  constructor() {
    try {
      this.config = EnvSchema.parse(process.env);
    } catch (error) {
      throw new Error(`Invalid environment configuration: ${error.message}`);
    }
  }

  get port(): number {
    return this.config.PORT;
  }

  get database(): string {
    return this.config.DATABASE_URL;
  }
}

Test Strategy

• Generate config module from contract
• Test with missing required env vars (should throw)
• Test with valid .env file (should succeed)
• Verify ConfigService injectable in AppModule
• Test config values accessible in services