Loki: Add scopedVars support in legend formatting for repeated variables (#27046)

* Pass scoped vars to createMetricLabel

* Add tests

* Refacotr

* Update tests

* Update test

public/app/plugins/datasource/loki/result_transformer.test.ts

@@ -1,5 +1,5 @@
 import { CircularDataFrame, FieldCache, FieldType, MutableDataFrame } from '@grafana/data';
-import { LokiStreamResult, LokiTailResponse, LokiStreamResponse, LokiResultType } from './types';
+import { LokiStreamResult, LokiTailResponse, LokiStreamResponse, LokiResultType, TransformerOptions } from './types';
 import * as ResultTransformer from './result_transformer';
 import { enhanceDataFrame } from './result_transformer';
 
@@ -114,6 +114,15 @@ describe('loki result transformer', () => {
       });
     });
   });
+  describe('createMetricLabel', () => {
+    it('should create correct label based on passed variables', () => {
+      const label = ResultTransformer.createMetricLabel({}, ({
+        scopedVars: { testLabel: { selected: true, text: 'label1', value: 'label1' } },
+        legendFormat: '{{$testLabel}}',
+      } as unknown) as TransformerOptions);
+      expect(label).toBe('label1');
+    });
+  });
 });
 
 describe('enhanceDataFrame', () => {