Added local observability stack with Prometheus, Grafana, and HTTP metrics dashboard

[GeorgeDiNicola]

Goal: To add observability using Prometheus & Grafana to a production-quality Go application, generate application traffic, and inspect core service health signals without additional manual setup. This repository can serve as boilerplate for running a Go application with CI/CD testing and observability best practices.

What Changed:

• Added Prometheus and Grafana docker images for local Docker-Compose coordination for the 3 services (including the go app)
• Added Prometheus scrape configuration and Grafana provisioning for datasources and dashboards
• Added HTTP metrics middleware for request counting and latency measurement
• Added tests for the metrics middleware
• Exposed the app metrics endpoint for Prometheus scraping
• Added a debug endpoint that intentionally returns a 500 response for observability testing
• Added a Grafana dashboard
• Updated the README with setup instructions, example queries, and guidance for using the local observability stack

Metric displays for the Grafana dashboard

• total request rate
• total request count by endpoint
• success rate
• request rate by endpoint and status grouping
• latency panels for average, p90, p95, and p99
• saturation/runtime panels for CPU, memory, goroutines, heap, GC pause, and file descriptor usage

Example visuals from the Grafana dashboard: