feat: migrate receiver to Fuego framework with OpenAPI generation

Replace net/http handlers with Fuego framework for automatic OpenAPI 3.0
spec generation. Add generated Go client package, OpenAPI extraction
script, and update Makefile with separate build/run targets for both
binaries.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cmd/receiver/main.go

@@ -1,16 +1,17 @@
+// ABOUTME: Entry point for the metrics receiver service.
+// ABOUTME: HTTP service using Fuego framework with automatic OpenAPI 3.0 generation.
 package main
 
 import (
-	"context"
 	"flag"
 	"fmt"
 	"log/slog"
-	"net/http"
 	"os"
-	"os/signal"
-	"syscall"
 	"time"
 
+	"github.com/getkin/kin-openapi/openapi3"
+	"github.com/go-fuego/fuego"
+
 	"edp.buildth.ing/DevFW-CICD/forgejo-runner-sizer/internal/receiver"
 )
 
@@ -39,42 +40,44 @@ func main() {
 	defer func() { _ = store.Close() }()
 
 	handler := receiver.NewHandler(store, logger, *readToken, *hmacKey, *tokenTTL)
-	mux := http.NewServeMux()
-	handler.RegisterRoutes(mux)
 
-	server := &http.Server{
-		Addr:         *addr,
-		Handler:      mux,
-		ReadTimeout:  10 * time.Second,
-		WriteTimeout: 10 * time.Second,
-	}
+	// Create Fuego server with OpenAPI configuration
+	s := fuego.NewServer(
+		fuego.WithAddr(*addr),
+		fuego.WithEngineOptions(
+			fuego.WithOpenAPIConfig(fuego.OpenAPIConfig{
+				PrettyFormatJSON: true,
+				JSONFilePath:     "docs/openapi.json",
+				SwaggerURL:       "/swagger",
+				Info: &openapi3.Info{
+					Title:       "Forgejo Runner Resource Collector API",
+					Version:     "1.0.0",
+					Description: "HTTP service that receives and stores CI/CD resource metrics from collectors, providing query and sizing recommendation APIs.",
+					Contact: &openapi3.Contact{
+						Name: "API Support",
+						URL:  "https://edp.buildth.ing/DevFW-CICD/forgejo-runner-sizer",
+					},
+					License: &openapi3.License{
+						Name: "Apache 2.0",
+						URL:  "http://www.apache.org/licenses/LICENSE-2.0.html",
+					},
+				},
+			}),
+		),
+	)
 
-	ctx, cancel := context.WithCancel(context.Background())
-	defer cancel()
-
-	sigChan := make(chan os.Signal, 1)
-	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
-
-	go func() {
-		sig := <-sigChan
-		logger.Info("received signal, shutting down", slog.String("signal", sig.String()))
-		cancel()
-
-		shutdownCtx, shutdownCancel := context.WithTimeout(context.Background(), 5*time.Second)
-		defer shutdownCancel()
-		_ = server.Shutdown(shutdownCtx)
-	}()
+	// Register routes
+	handler.RegisterRoutes(s)
 
 	logger.Info("starting metrics receiver",
 		slog.String("addr", *addr),
 		slog.String("db", *dbPath),
+		slog.String("swagger", fmt.Sprintf("http://localhost%s/swagger", *addr)),
 	)
 
-	if err := server.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+	// Run server (handles graceful shutdown)
+	if err := s.Run(); err != nil {
 		fmt.Fprintf(os.Stderr, "error: %v\n", err)
 		os.Exit(1)
 	}
-
-	<-ctx.Done()
-	logger.Info("receiver stopped gracefully")
 }