improve README

Author: massimosiani

README.md

@@ -4,6 +4,6 @@
 
 A tiny integration library for Natchez and Akka Http.
 
-Only a server middleware has been implemented so far.
+Examples of usage are given for both the client and the server. A Tapir integration is also shown.
 
 Head over the [site](http://massimosiani.github.io/natchez-akka-http/) for further information.

natchez-akka-http/src/main/scala/natchez/akka/http/NatchezAkkaHttp.scala

@@ -103,8 +103,7 @@ object NatchezAkkaHttp {
           .put(("cancelled", TraceValue.BooleanValue(true)), Tags.error(true))
     }
 
-  private def addErrorFields[F[_]: Trace](e: Throwable): F[Unit] =
-    Trace[F].put(Tags.error(true), "error.message" -> e.getMessage())
+  private def addErrorFields[F[_]: Trace](e: Throwable): F[Unit] = Trace[F].attachError(e)
 
   private def addRequestFields[F[_]: Trace](req: HttpRequest): F[Unit] =
     Trace[F].put(Tags.http.method(req.method.name), Tags.http.url(req.uri.toString()))