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/log.go

@@ -0,0 +1,75 @@
+package server
+
+import (
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/qdm12/golibs/logging"
+)
+
+func withLogMiddleware(childHandler http.Handler, logger logging.Logger, enabled bool) *logMiddleware {
+	return &logMiddleware{
+		childHandler: childHandler,
+		logger:       logger,
+		timeNow:      time.Now,
+		enabled:      enabled,
+	}
+}
+
+type logMiddleware struct {
+	childHandler http.Handler
+	logger       logging.Logger
+	timeNow      func() time.Time
+	enabled      bool
+	enabledMu    sync.RWMutex
+}
+
+func (m *logMiddleware) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	if !m.isEnabled() {
+		m.childHandler.ServeHTTP(w, r)
+		return
+	}
+	tStart := m.timeNow()
+	statefulWriter := &statefulResponseWriter{httpWriter: w}
+	m.childHandler.ServeHTTP(statefulWriter, r)
+	duration := m.timeNow().Sub(tStart)
+	m.logger.Info("%d %s %s wrote %dB to %s in %s",
+		statefulWriter.statusCode, r.Method, r.RequestURI, statefulWriter.length, r.RemoteAddr, duration)
+}
+
+func (m *logMiddleware) setEnabled(enabled bool) {
+	m.enabledMu.Lock()
+	defer m.enabledMu.Unlock()
+	m.enabled = enabled
+}
+
+func (m *logMiddleware) isEnabled() (enabled bool) {
+	m.enabledMu.RLock()
+	defer m.enabledMu.RUnlock()
+	return m.enabled
+}
+
+type statefulResponseWriter struct {
+	httpWriter http.ResponseWriter
+	statusCode int
+	length     int
+}
+
+func (w *statefulResponseWriter) Write(b []byte) (n int, err error) {
+	n, err = w.httpWriter.Write(b)
+	if w.statusCode == 0 {
+		w.statusCode = http.StatusOK
+	}
+	w.length += n
+	return n, err
+}
+
+func (w *statefulResponseWriter) WriteHeader(statusCode int) {
+	w.statusCode = statusCode
+	w.httpWriter.WriteHeader(statusCode)
+}
+
+func (w *statefulResponseWriter) Header() http.Header {
+	return w.httpWriter.Header()
+}