feat: Add comprehensive REST API integration patterns

Integration/REST API Patterns/README.md

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+# Advanced REST API Integration Patterns
+
+This collection provides comprehensive patterns and best practices for integrating ServiceNow with external systems using REST APIs.
+
+## Overview
+
+Modern ServiceNow integrations require robust, scalable, and maintainable REST API patterns. These snippets demonstrate enterprise-grade integration techniques including error handling, authentication, rate limiting, and data transformation.
+
+## Integration Patterns Included
+
+### Authentication & Security
+- **OAuth 2.0 Integration**: Complete OAuth flow implementation
+- **API Key Management**: Secure API key handling and rotation
+- **JWT Token Handling**: JSON Web Token authentication patterns
+- **Certificate-Based Auth**: Mutual TLS authentication examples
+
+### Error Handling & Resilience
+- **Retry Mechanisms**: Exponential backoff and circuit breaker patterns
+- **Timeout Management**: Proper timeout configuration and handling
+- **Error Classification**: Distinguishing between retryable and non-retryable errors
+- **Fallback Strategies**: Graceful degradation patterns
+
+### Data Processing
+- **Pagination Handling**: Efficient large dataset processing
+- **Batch Operations**: Bulk data synchronization patterns
+- **Data Transformation**: JSON mapping and field transformation
+- **Validation & Sanitization**: Input/output data validation
+
+### Performance Optimization
+- **Connection Pooling**: Reusable connection management
+- **Caching Strategies**: Response caching and invalidation
+- **Asynchronous Processing**: Non-blocking API calls
+- **Rate Limiting**: API quota management and throttling
+
+## Architecture Patterns
+
+### Outbound Integrations
+- RESTMessageV2 optimization
+- Scheduled job integration patterns
+- Event-driven API calls
+- Real-time data synchronization
+
+### Inbound Integrations
+- Scripted REST API best practices
+- Webhook handling patterns
+- API gateway integration
+- Authentication middleware
+
+## Snippets Overview
+
+1. **oauth2_integration.js** - Complete OAuth 2.0 implementation with token management
+2. **retry_mechanism.js** - Advanced retry, circuit breaker, and error handling patterns
+3. **rate_limiting.js** - Multiple rate limiting strategies (token bucket, sliding window, fixed window)
+4. **response_caching.js** - Intelligent API response caching with compression and encryption
+5. **batch_synchronization.js** - Efficient bulk data processing (coming soon)
+6. **data_transformation.js** - JSON mapping and validation utilities (coming soon)
+7. **async_processing.js** - Asynchronous API call patterns (coming soon)
+
+## Pattern Details
+
+### 🔐 OAuth 2.0 Integration (`oauth2_integration.js`)
+- Authorization code flow with PKCE support
+- Automatic token refresh and secure storage
+- State parameter validation for CSRF protection
+- Authenticated API request wrapper
+
+### 🔄 Retry Mechanism (`retry_mechanism.js`) 
+- Exponential backoff with configurable jitter
+- Circuit breaker pattern implementation
+- Parallel API calls with retry support
+- Intelligent error classification
+
+### ⏱️ Rate Limiting (`rate_limiting.js`)
+- Token bucket algorithm for burst allowance
+- Sliding window for strict rate enforcement
+- Fixed window for traditional limiting
+- Per-user and per-endpoint controls
+
+### 💾 Response Caching (`response_caching.js`)
+- LRU, LFU, and TTL eviction policies
+- Optional compression and encryption
+- Tag-based invalidation strategies
+- Performance statistics and monitoring
+
+## Best Practices
+
+- Always implement proper error handling and logging
+- Use authentication tokens securely with proper rotation
+- Implement rate limiting to respect API quotas
+- Design for idempotency to handle duplicate operations
+- Use pagination for large datasets
+- Implement circuit breakers for external service failures
+- Cache responses when appropriate to reduce API calls
+- Validate and sanitize all input/output data
+
+## Security Considerations
+
+- Store credentials securely using ServiceNow's credential store
+- Use HTTPS for all API communications
+- Implement proper input validation to prevent injection attacks
+- Log security events for monitoring and compliance
+- Rotate authentication tokens regularly
+- Use least privilege principle for API access
+
+## Monitoring & Observability
+
+- Implement comprehensive logging for troubleshooting
+- Track API performance metrics and SLA compliance
+- Monitor error rates and implement alerting
+- Use correlation IDs for distributed tracing
+- Implement health checks for external systems
+
+## Related Documentation
+
+- [ServiceNow REST API Documentation](https://developer.servicenow.com/dev.do#!/reference/api/tokyo/rest/)
+- [RESTMessageV2 API Reference](https://developer.servicenow.com/dev.do#!/reference/api/tokyo/server/no-namespace/c_RESTMessageV2API)