added WithHeaders method to MetricsQueryRequest interface

Signed-off-by: Miguel Ángel Ortuño <ortuman@gmail.com>

pkg/frontend/querymiddleware/codec.go

@@ -124,6 +124,8 @@ type MetricsQueryRequest interface {
 	// WithQuery clones the current request with a different query; returns error if query parse fails.
 	// Implementations must ensure minT and maxT are recalculated when the query changes.
 	WithQuery(string) (MetricsQueryRequest, error)
+	// WithHeaders clones the current request with different headers.
+	WithHeaders([]*PrometheusHeader) MetricsQueryRequest
 	// WithExpr clones the current `PrometheusRangeQueryRequest` with a new query expression.
 	// Implementations must ensure minT and maxT are recalculated when the query changes.
 	WithExpr(parser.Expr) MetricsQueryRequest

pkg/frontend/querymiddleware/model_extra.go

@@ -184,6 +184,13 @@ func (r *PrometheusRangeQueryRequest) WithQuery(query string) (MetricsQueryReque
 	return &newRequest, nil
 }
 
+// WithHeaders clones the current `PrometheusRangeQueryRequest` with new headers.
+func (r *PrometheusRangeQueryRequest) WithHeaders(headers []*PrometheusHeader) MetricsQueryRequest {
+	newRequest := *r
+	newRequest.headers = headers
+	return &newRequest
+}
+
 // WithExpr clones the current `PrometheusRangeQueryRequest` with a new query expression.
 func (r *PrometheusRangeQueryRequest) WithExpr(queryExpr parser.Expr) MetricsQueryRequest {
 	newRequest := *r
@@ -376,6 +383,13 @@ func (r *PrometheusInstantQueryRequest) WithQuery(query string) (MetricsQueryReq
 	return &newRequest, nil
 }
 
+// WithHeaders clones the current `PrometheusRangeQueryRequest` with new headers.
+func (r *PrometheusInstantQueryRequest) WithHeaders(headers []*PrometheusHeader) MetricsQueryRequest {
+	newRequest := *r
+	newRequest.headers = headers
+	return &newRequest
+}
+
 // WithExpr clones the current `PrometheusInstantQueryRequest` with a new query expression.
 func (r *PrometheusInstantQueryRequest) WithExpr(queryExpr parser.Expr) MetricsQueryRequest {
 	newRequest := *r