chore(settings): refactor settings processing (#756)

- Better settings tree structure logged using `qdm12/gotree`
- Read settings from environment variables, then files, then secret files
- Settings methods to default them, merge them and override them
- `DNS_PLAINTEXT_ADDRESS` default changed to `127.0.0.1` to use DoT. Warning added if set to something else.
- `HTTPPROXY_LISTENING_ADDRESS` instead of `HTTPPROXY_PORT` (with retro-compatibility)

internal/publicip/ticker.go

@@ -16,7 +16,7 @@ func (l *Loop) RunRestartTicker(ctx context.Context, done chan<- struct{}) {
 	timer := time.NewTimer(time.Hour)
 	timer.Stop() // 1 hour, cannot be a race condition
 	timerIsStopped := true
-	if period := l.state.GetSettings().Period; period > 0 {
+	if period := *l.state.GetSettings().Period; period > 0 {
 		timerIsStopped = false
 		timer.Reset(period)
 	}
@@ -31,13 +31,13 @@ func (l *Loop) RunRestartTicker(ctx context.Context, done chan<- struct{}) {
 		case <-timer.C:
 			lastTick = l.timeNow()
 			_, _ = l.ApplyStatus(ctx, constants.Running)
-			timer.Reset(l.state.GetSettings().Period)
+			timer.Reset(*l.state.GetSettings().Period)
 		case <-l.updateTicker:
 			if !timerIsStopped && !timer.Stop() {
 				<-timer.C
 			}
 			timerIsStopped = true
-			period := l.state.GetSettings().Period
+			period := *l.state.GetSettings().Period
 			if period == 0 {
 				continue
 			}