feat: Add Advanced Scripted REST API Patterns

- API Gateway Pattern with routing and rate limiting
- Authentication & Authorization Framework with multiple strategies
- Data Transformation Pipeline with validation and mapping
- Error Handling & Resilience with circuit breaker and retry logic

Features:
- Centralized API gateway with request transformation
- Multi-strategy auth (OAuth2, JWT, API Keys, Basic)
- Flexible data transformation and validation
- Circuit breaker, retry mechanisms, and health checks
- Comprehensive error handling and graceful degradation
- Enterprise-grade security and monitoring

Author: ashvin2005

Integration/Scripted REST APIs/Advanced API Patterns/README.md

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+# Advanced Scripted REST API Patterns
+
+This collection demonstrates enterprise-grade Scripted REST API patterns for ServiceNow, focusing on security, performance, and maintainability best practices.
+
+## 🎯 Features
+
+### 1. **API Gateway Pattern** (`api_gateway_pattern.js`)
+- Centralized request routing and transformation
+- Rate limiting and throttling
+- Request/response validation
+- API versioning support
+- Comprehensive logging and monitoring
+
+### 2. **Authentication & Authorization Framework** (`auth_framework.js`)
+- Multiple authentication strategies (OAuth2, JWT, API Keys)
+- Role-based access control (RBAC)
+- Resource-level permissions
+- Token validation and refresh
+- Security audit logging
+
+### 3. **Data Transformation Pipeline** (`data_transformation_pipeline.js`)
+- Flexible input/output data mapping
+- Schema validation and transformation
+- Data sanitization and normalization
+- Custom field processors
+- Batch processing capabilities
+
+### 4. **Error Handling & Resilience** (`error_handling_resilience.js`)
+- Comprehensive error response patterns
+- Circuit breaker implementation
+- Retry mechanisms with exponential backoff
+- Graceful degradation strategies
+- Health check endpoints
+
+### 5. **Performance Optimization** (`performance_optimization.js`)
+- Intelligent caching strategies
+- Database query optimization
+- Response compression and pagination
+- Asynchronous processing patterns
+- Resource pooling
+
+## 🚀 Key Benefits
+
+- **Security**: Multi-layered security with authentication, authorization, and validation
+- **Performance**: Optimized for high-throughput scenarios with caching and pagination
+- **Reliability**: Robust error handling with circuit breakers and retry logic
+- **Scalability**: Designed for enterprise-scale deployments
+- **Maintainability**: Clean, modular code with comprehensive documentation
+
+## 📋 Implementation Guidelines
+
+1. **Security First**: Always validate inputs and implement proper authentication
+2. **Performance**: Use caching and pagination for large datasets
+3. **Error Handling**: Provide meaningful error messages and proper HTTP status codes
+4. **Documentation**: Auto-generate OpenAPI/Swagger documentation
+5. **Testing**: Include comprehensive test suites for all endpoints
+
+## 🔧 Usage Requirements
+
+- ServiceNow Madrid or later
+- Proper REST API roles and permissions
+- Understanding of HTTP protocols and REST principles
+- Knowledge of ServiceNow scripting and GlideRecord APIs
+
+## 📖 Best Practices
+
+- Follow RESTful design principles
+- Use appropriate HTTP methods and status codes
+- Implement proper input validation and sanitization
+- Use structured logging for debugging and monitoring
+- Consider API versioning from the start
+- Implement rate limiting to prevent abuse
+
+## 🔒 Security Considerations
+
+- Always validate and sanitize input data
+- Implement proper authentication and authorization
+- Use HTTPS for all API communications
+- Log security events for audit purposes
+- Regularly review and update security configurations
+
+---
+
+*Part of the ServiceNow Code Snippets collection - Advanced Scripted REST API Patterns*