Loops and HTTP control server rework (#308)

- CRUD REST HTTP server
- `/v1` HTTP server prefix
- Retrocompatible with older routes (redirects to v1 or handles the requests directly)
- DNS, Updater and Openvpn refactored to have a REST-like state with new methods to change their states synchronously
- Openvpn, Unbound and Updater status, see #287

internal/server/handlerv1.go

@@ -0,0 +1,58 @@
+package server
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/qdm12/gluetun/internal/models"
+	"github.com/qdm12/golibs/logging"
+)
+
+func newHandlerV1(logger logging.Logger, buildInfo models.BuildInformation,
+	openvpn, dns, updater http.Handler) http.Handler {
+	return &handlerV1{
+		logger:    logger,
+		buildInfo: buildInfo,
+		openvpn:   openvpn,
+		dns:       dns,
+		updater:   updater,
+	}
+}
+
+type handlerV1 struct {
+	logger    logging.Logger
+	buildInfo models.BuildInformation
+	openvpn   http.Handler
+	dns       http.Handler
+	updater   http.Handler
+}
+
+func (h *handlerV1) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	switch {
+	case r.RequestURI == "/version" && r.Method == http.MethodGet:
+		h.getVersion(w)
+	case strings.HasPrefix(r.RequestURI, "/openvpn"):
+		h.openvpn.ServeHTTP(w, r)
+	case strings.HasPrefix(r.RequestURI, "/dns"):
+		h.dns.ServeHTTP(w, r)
+	case strings.HasPrefix(r.RequestURI, "/updater"):
+		h.updater.ServeHTTP(w, r)
+	default:
+		errString := fmt.Sprintf("%s %s not found", r.Method, r.RequestURI)
+		http.Error(w, errString, http.StatusNotFound)
+	}
+}
+
+func (h *handlerV1) getVersion(w http.ResponseWriter) {
+	data, err := json.Marshal(h.buildInfo)
+	if err != nil {
+		h.logger.Warn(err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+	if _, err := w.Write(data); err != nil {
+		h.logger.Warn(err)
+	}
+}