feat: add slog logging (#432)

* feat(op): user slog for logging

integrate with golang.org/x/exp/slog for logging.
provide a middleware for request scoped logging.

BREAKING CHANGES:

1. OpenIDProvider and sub-interfaces get a Logger()
method to return the configured logger;
2. AuthRequestError now takes the complete Authorizer,
instead of only the encoder. So that it may use its Logger() method.
3. RequestError now takes a Logger as argument.

* use zitadel/logging

* finish op and testing
without middleware for now

* minimum go version 1.19

* update go mod

* log value testing only on go 1.20 or later

* finish the RP and example

* ping logging release

example/server/main.go

@@ -2,11 +2,12 @@ package main
 
 import (
 	"fmt"
-	"log"
 	"net/http"
+	"os"
 
 	"github.com/zitadel/oidc/v3/example/server/exampleop"
 	"github.com/zitadel/oidc/v3/example/server/storage"
+	"golang.org/x/exp/slog"
 )
 
 func main() {
@@ -20,16 +21,22 @@ func main() {
 	// in this example it will be handled in-memory
 	storage := storage.NewStorage(storage.NewUserStore(issuer))
 
-	router := exampleop.SetupServer(issuer, storage)
+	logger := slog.New(
+		slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{
+			AddSource: true,
+			Level:     slog.LevelDebug,
+		}),
+	)
+	router := exampleop.SetupServer(issuer, storage, logger)
 
 	server := &http.Server{
 		Addr:    ":" + port,
 		Handler: router,
 	}
-	log.Printf("server listening on http://localhost:%s/", port)
-	log.Println("press ctrl+c to stop")
+	logger.Info("server listening, press ctrl+c to stop", "addr", fmt.Sprintf("http://localhost:%s/", port))
 	err := server.ListenAndServe()
-	if err != nil {
-		log.Fatal(err)
+	if err != http.ErrServerClosed {
+		logger.Error("server terminated", "error", err)
+		os.Exit(1)
 	}
 }