fix: always write detected_level when enabled, even if unknown (#14464)

Co-authored-by: shantanualshi <shantanu.alshi@grafana.com>

Author: trevorwhitney

pkg/distributor/distributor.go

@@ -502,7 +502,7 @@ func (d *Distributor) Push(ctx context.Context, req *logproto.PushRequest) (*log
 					} else {
 						logLevel = detectLogLevelFromLogEntry(entry, structuredMetadata)
 					}
-					if logLevel != constants.LogLevelUnknown && logLevel != "" {
+					if logLevel != "" {
 						entry.StructuredMetadata = append(entry.StructuredMetadata, logproto.LabelAdapter{
 							Name:  constants.LevelLabel,
 							Value: logLevel,

pkg/distributor/distributor_test.go

@@ -1640,7 +1640,7 @@ func Test_DetectLogLevels(t *testing.T) {
 		require.NoError(t, err)
 		topVal := ingester.Peek()
 		require.Equal(t, `{foo="bar"}`, topVal.Streams[0].Labels)
-		require.Len(t, topVal.Streams[0].Entries[0].StructuredMetadata, 0)
+		require.Len(t, topVal.Streams[0].Entries[0].StructuredMetadata, 1)
 	})
 
 	t.Run("log level detection enabled and warn logs", func(t *testing.T) {