config.rs - Environment Configuration Management

Requirements and Dataflow

Loads application configuration from environment variables with fallback defaults
Validates production-specific security requirements and constraints
Manages OAuth provider credentials and TLS certificate configuration
Provides differential privacy parameters and security policy settings
Ensures configuration safety across different deployment environments

Environment Parsing: Converts environment variables to strongly-typed configuration structures
Production Validation: Enforces security policies and prevents weak configurations in production
OAuth Management: Handles Apple and GitHub OAuth provider configuration with validation
TLS Configuration: Manages SSL/TLS settings including Let's Encrypt integration
Security Policies: Defines JWT secrets, CORS policies, rate limiting, and privacy parameters
Development Defaults: Provides sensible defaults for local development environments

Config struct: Comprehensive configuration container with all application settings
Environment enum: Deployment environment classification (Development, Staging, Production)
from_env(): Main configuration loading function with environment variable parsing
validate_production_safety(): Production-specific security validation
require_in_production(): Helper for mandatory production configuration values

Environment Variables → Typed Config: Parses and validates environment variables
Default Value Application: Applies environment-appropriate defaults where values are missing
OAuth Credential Validation: Verifies OAuth provider configuration completeness
TLS Setting Validation: Ensures proper certificate configuration for HTTPS
Security Policy Enforcement: Validates JWT secrets, CORS origins, and privacy parameters
Production Safety Checks: Prevents deployment with insecure configuration values

Environment System: Reads from process environment variables and .env files
OAuth Providers: Validates Apple and GitHub OAuth application credentials
TLS Infrastructure: Coordinates with certificate management and HTTPS setup
Database Layer: Provides database connection URL and pooling configuration
Cache System: Configures Redis/cache connection parameters
Security Middleware: Supplies JWT secrets, CORS policies, and rate limiting settings
Privacy Systems: Provides differential privacy epsilon/delta parameters

Environment-Driven Configuration: Deployment-specific behavior through environment variables
Validation Layers: Multi-stage validation with development vs production requirements
Fail-Fast Strategy: Early configuration validation prevents runtime failures
Security-First Design: Production safety validation prevents insecure deployments
Provider Abstraction: Unified OAuth provider configuration pattern
Privacy by Design: Built-in differential privacy parameter configuration