Fix header format conversion used in Resources (#39654)

We were not copying the metadata.revision field.

api/types/header/convert/legacy/header.go

@@ -30,5 +30,6 @@ func FromHeaderMetadata(metadata header.Metadata) types.Metadata {
 		Expires:     &metadata.Expires,
 		Description: metadata.Description,
 		Labels:      metadata.Labels,
+		Revision:    metadata.Revision,
 	}
 }

api/types/header/convert/legacy/header_test.go

@@ -0,0 +1,52 @@
+/*
+Copyright 2024 Gravitational, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package legacy
+
+import (
+	"testing"
+	"time"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/stretchr/testify/require"
+
+	"github.com/gravitational/teleport/api/types"
+	"github.com/gravitational/teleport/api/types/header"
+)
+
+func TestFromHeaderMetadata(t *testing.T) {
+	expires := time.Now()
+
+	expectedHeader := types.Metadata{
+		ID:          12345,
+		Name:        "name",
+		Expires:     &expires,
+		Description: "description",
+		Labels:      map[string]string{"label": "value"},
+		Revision:    "revision",
+	}
+
+	converted := FromHeaderMetadata(header.Metadata{
+		Name:        "name",
+		Description: "description",
+		Labels:      map[string]string{"label": "value"},
+		Expires:     expires,
+		ID:          12345,
+		Revision:    "revision",
+	})
+
+	require.Empty(t, cmp.Diff(expectedHeader, converted))
+}