add jsonhttp.NotFoundHandler and use it in api and debug api

pkg/api/router.go

@@ -18,9 +18,7 @@ import (
 
 func (s *server) setupRouting() {
 	router := mux.NewRouter()
-	router.NotFoundHandler = http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
-		jsonhttp.NotFound(w, nil)
-	})
+	router.NotFoundHandler = http.HandlerFunc(jsonhttp.NotFoundHandler)
 
 	router.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
 		fmt.Fprintln(w, "Ethereum Swarm Bee")

pkg/debugapi/router.go

@@ -27,9 +27,7 @@ func (s *server) setupRouting() {
 	))
 
 	router := mux.NewRouter()
-	router.NotFoundHandler = http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
-		jsonhttp.NotFound(w, nil)
-	})
+	router.NotFoundHandler = http.HandlerFunc(jsonhttp.NotFoundHandler)
 
 	router.Handle("/debug/pprof/", http.HandlerFunc(pprof.Index))
 	router.Handle("/debug/pprof/cmdline", http.HandlerFunc(pprof.Cmdline))

pkg/jsonhttp/handlers.go

@@ -15,3 +15,7 @@ type MethodHandler map[string]http.Handler
 func (h MethodHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	web.HandleMethods(h, `{"message":"Method Not Allowed","code":405}`, DefaultContentTypeHeader, w, r)
 }
+
+func NotFoundHandler(w http.ResponseWriter, _ *http.Request) {
+	NotFound(w, nil)
+}