all: imp response; fmt

internal/aghhttp/aghhttp.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"net/http"
 
+	"github.com/AdguardTeam/AdGuardHome/internal/version"
 	"github.com/AdguardTeam/golibs/log"
 )
 
@@ -28,3 +29,9 @@ func Error(r *http.Request, w http.ResponseWriter, code int, format string, args
 	log.Error("%s %s: %s", r.Method, r.URL, text)
 	http.Error(w, text, code)
 }
+
+// UserAgent returns the ID of the service as a User-Agent string.  It can also
+// be used as the value of the Server HTTP header.
+func UserAgent() (ua string) {
+	return fmt.Sprintf("AdGuardDNS/%s", version.Version())
+}

internal/aghhttp/header.go

@@ -0,0 +1,21 @@
+package aghhttp
+
+// HTTP Headers
+
+// HTTP header name constants.
+//
+// TODO(a.garipov): Remove unused.
+const (
+	HdrNameAcceptEncoding           = "Accept-Encoding"
+	HdrNameAccessControlAllowOrigin = "Access-Control-Allow-Origin"
+	HdrNameContentType              = "Content-Type"
+	HdrNameContentEncoding          = "Content-Encoding"
+	HdrNameServer                   = "Server"
+	HdrNameTrailer                  = "Trailer"
+	HdrNameUserAgent                = "User-Agent"
+)
+
+// HTTP header value constants.
+const (
+	HdrValApplicationJSON = "application/json"
+)