refactor(config): reduce references to config.GetInstance()

internal/autocert/provider.go

@@ -10,6 +10,7 @@ import (
 	"path"
 	"slices"
 	"strings"
+	"sync/atomic"
 	"time"
 
 	"github.com/go-acme/lego/v4/certificate"
@@ -49,6 +50,9 @@ const (
 	requestCooldownDuration = 15 * time.Second
 )
 
+// could be nil
+var ActiveProvider atomic.Pointer[Provider]
+
 func NewProvider(cfg *Config, user *User, legoCfg *lego.Config) *Provider {
 	return &Provider{
 		cfg:     cfg,