AuthN: tune logging (#60917)

* AuthN: remove comment

* AuthN: Only start trace if valid authentication client is used

pkg/services/authn/authnimpl/service.go

@@ -77,43 +77,28 @@ type Service struct {
 }
 
 func (s *Service) Authenticate(ctx context.Context, client string, r *authn.Request) (*authn.Identity, bool, error) {
-	ctx, span := s.tracer.Start(ctx, "authn.Authenticate")
-	defer span.End()
-
-	span.SetAttributes("authn.client", client, attribute.Key("authn.client").String(client))
-	logger := s.log.FromContext(ctx)
-
 	c, ok := s.clients[client]
 	if !ok {
-		logger.Debug("auth client not found", "client", client)
-		span.AddEvents([]string{"message"}, []tracing.EventValue{{Str: "auth client is not configured"}})
 		return nil, false, nil
 	}
 
 	if !c.Test(ctx, r) {
-		logger.Debug("auth client cannot handle request", "client", client)
-		span.AddEvents([]string{"message"}, []tracing.EventValue{{Str: "auth client cannot handle request"}})
 		return nil, false, nil
 	}
 
+	ctx, span := s.tracer.Start(ctx, "authn.Authenticate")
+	defer span.End()
+	span.SetAttributes("authn.client", client, attribute.Key("authn.client").String(client))
+
 	r.OrgID = orgIDFromRequest(r)
 	identity, err := c.Authenticate(ctx, r)
 	if err != nil {
-		logger.Warn("auth client could not authenticate request", "client", client, "error", err)
+		s.log.FromContext(ctx).Warn("auth client could not authenticate request", "client", client, "error", err)
 		span.AddEvents([]string{"message"}, []tracing.EventValue{{Str: "auth client could not authenticate request"}})
 		return nil, true, err
 	}
 
-	// FIXME: We want to perform common authentication operations here.
-	// We will add them as we start to implement clients that requires them.
-	// Those operations can be Syncing user, syncing teams, create a session etc.
-	// We would need to check what operations a client support and also if they are requested
-	// because for e.g. basic auth we want to create a session if the call is coming from the
-	// login handler, but if we want to perform basic auth during a request (called from contexthandler) we don't
-	// want a session to be created.
-
 	params := c.ClientParams()
-
 	for _, hook := range s.postAuthHooks {
 		if err := hook(ctx, params, identity, r); err != nil {
 			return nil, false, err