feat: Add payment retry sample with Temporal workflow implementation

[alvidofaisal]

What changed?

Added a comprehensive payment retry sample application that demonstrates how to implement robust payment processing workflows using Temporal. The sample includes:

• Payment workflow with configurable retry policies and timeout handling
• Payment activity implementation with proper error handling
• Complete Docker containerization setup
• Kubernetes Helm charts for production deployment
• Grafana dashboard for monitoring payment workflow metrics
• Go module configuration with necessary dependencies

Why?

This sample addresses a common real-world use case where payment processing requires resilient retry logic and proper error handling. Payment systems often need to handle temporary failures, network issues, and third-party service outages gracefully. This example provides developers with:

• A practical reference implementation for payment processing workflows
• Best practices for implementing retry strategies in financial applications
• Production-ready deployment configurations
• Observability setup for monitoring payment success/failure rates
• A foundation that can be adapted for various payment processing scenarios

How did you test it?

• [x] built
• [x] run locally and tested manually
• [ ] covered by existing tests
• [ ] added new unit test(s)
• [ ] added new functional test(s)

Potential risks

• This is a sample application with no impact on production systems
• New dependencies are isolated to the sample's go.mod file
• Docker and Helm configurations are self-contained within the sample directory

[CLAassistant]

All committers have signed the CLA.

[github-actions[bot]]

This PR was marked as stale. Please update or close it.