chore: Make example/server usable for tests (#205)

* internal -> storage; split users into an interface

* move example/server/*.go to example/server/exampleop/

* export all User fields

* storage -> Storage

* example server now passes tests

example/server/main.go

@@ -0,0 +1,32 @@
+package main
+
+import (
+	"context"
+	"log"
+	"net/http"
+
+	"github.com/zitadel/oidc/example/server/exampleop"
+	"github.com/zitadel/oidc/example/server/storage"
+)
+
+func main() {
+	ctx := context.Background()
+
+	// the OpenIDProvider interface needs a Storage interface handling various checks and state manipulations
+	// this might be the layer for accessing your database
+	// in this example it will be handled in-memory
+	storage := storage.NewStorage(storage.NewUserStore())
+
+	port := "9998"
+	router := exampleop.SetupServer(ctx, "http://localhost:"+port, storage)
+
+	server := &http.Server{
+		Addr:    ":" + port,
+		Handler: router,
+	}
+	err := server.ListenAndServe()
+	if err != nil {
+		log.Fatal(err)
+	}
+	<-ctx.Done()
+}