move protocol-related code into internal/protocols (#2572)

internal/protocols/httpserv/handler_server_header.go

@@ -0,0 +1,15 @@
+package httpserv
+
+import (
+	"net/http"
+)
+
+// set the Server header.
+type handlerServerHeader struct {
+	http.Handler
+}
+
+func (h *handlerServerHeader) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Server", "mediamtx")
+	h.Handler.ServeHTTP(w, r)
+}