feat(cmd/anubis): capture ja4h fingerprints (#834)

This is not used yet, but it will be part of a larger strategy around
adding/removing weight based on JA4H (and other) fingerprint matches
with Thoth.

Signed-off-by: Xe Iaso <me@xeiaso.net>

internal/ja4h.go

@@ -0,0 +1,14 @@
+package internal
+
+import (
+	"net/http"
+
+	"github.com/lum8rjack/go-ja4h"
+)
+
+func JA4H(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		r.Header.Add("X-Http-Fingerprint-JA4H", ja4h.JA4H(r))
+		next.ServeHTTP(w, r)
+	})
+}