Add Configuration Module with Environment Schema Validation

[RUKAYAT-CODER]

⚙️ Add Configuration Module with Environment Schema Validation

Module: Common / Configuration
Type: Feature / Infrastructure

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📖 Overview

This PR introduces a centralized, typed configuration module that loads environment variables, validates them at application startup, and exposes a safe, ergonomic API for accessing configuration across the app.

The goal is to fail fast on misconfiguration, eliminate scattered process.env usage, and provide a single source of truth for all environment-dependent settings.

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🎯 Goals

• Provide typed, safe access to configuration values
• Validate environment variables at boot time
• Exit early with clear, actionable errors on invalid config
• Support multiple environments (development, test, production)
• Offer an ergonomic API for consumers (e.g. config.getDatabaseUrl())

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🧩 Solution Overview

Config Module

• ConfigModule and ConfigService added under:
  • src/common/config (or src/config)
• Loads environment files based on NODE_ENV:
  • .env
  • .env.development
  • .env.test
  • .env.production
• Registered globally (or imported into AppModule) for app-wide access

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🔐 Environment Validation

• Environment variables are validated before app bootstrap
• Application exits immediately if validation fails
• Errors clearly indicate:
  • Which key is missing or invalid
  • Why validation failed

Validation Strategy

One of the following approaches is used:

• Option A: Joi
  • Centralized schema (validationSchema.ts)
  • Concise, declarative validation
• Option B: class-validator
  • ConfigDto with typed fields
  • Validation performed after env loading

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🧠 Typed Access Pattern

• Centralized config keys (e.g. constants or enum)
• No direct process.env access outside the ConfigModule
• Typed getters exposed by ConfigService, such as:
  • getDatabaseUrl()
  • getRedisUrl()
  • getPort()
  • getNodeEnv()

Example usage:

constructor(private readonly config: ConfigService) {}

const dbUrl = this.config.getDatabaseUrl();

close #75

[RUKAYAT-CODER]

Created PR kindly review