refactor: restore "First stage of access logging middleware."

This reverts commit 82651985c4.

middlewares/accesslog/capture_request_reader.go

@@ -0,0 +1,18 @@
+package accesslog
+
+import "io"
+
+type captureRequestReader struct {
+	source io.ReadCloser
+	count  int64
+}
+
+func (r *captureRequestReader) Read(p []byte) (int, error) {
+	n, err := r.source.Read(p)
+	r.count += int64(n)
+	return n, err
+}
+
+func (r *captureRequestReader) Close() error {
+	return r.source.Close()
+}