Traffic Policy Engine now supports dynamic configuration with CEL Interpolation

CEL Interpolation is a powerful capability that allows for dynamic configuration with ngrok's Traffic Policy Module by embedding variables and expressions in actions using the ${CEL} format. This enables more flexibility and adaptability in traffic policy configurations, enriching rules with connection, request, or response details through CEL variables and expressions. By leveraging CEL Interpolation, users can create custom responses or perform specific actions based on request data, such as adding dynamic headers to HTTP requests. The capability is supported only in specific policy action configuration fields and treats everything inside curly brackets as CEL expressions, including functions like split and join.