cmd/swarm, swarm: added access control functionality (#17404)

Co-authored-by: Janos Guljas <janos@resenje.org>
Co-authored-by: Anton Evangelatov <anton.evangelatov@gmail.com>
Co-authored-by: Balint Gabor <balint.g@gmail.com>

swarm/sctx/sctx.go

@@ -1,7 +1,22 @@
 package sctx
 
+import "context"
+
 type ContextKey int
 
 const (
 	HTTPRequestIDKey ContextKey = iota
+	requestHostKey
 )
+
+func SetHost(ctx context.Context, domain string) context.Context {
+	return context.WithValue(ctx, requestHostKey, domain)
+}
+
+func GetHost(ctx context.Context) string {
+	v, ok := ctx.Value(requestHostKey).(string)
+	if ok {
+		return v
+	}
+	return ""
+}