[exporter/elasticsearch] Update the ECS mode metrics data point hasher to exclude the elasticsearch.mapping.hints attribute (open-telemetry#45887)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
This PR updates the ECS mode metrics data point hasher to exclude the
`elasticsearch.mapping.hints` attribute.
This is helpful for aggregated metrics generated by the
https://github.com/elastic/opentelemetry-collector-components/tree/main/connector/elasticapmconnector,
since it generates metrics where the only difference is the
`elasticsearch.mapping.hints` attribute value.

This also aligns with the OTEL mode metrics data point hasher.

Assisted-by: Claude Opus 4.5

<!--Describe what testing was performed and which tests were added.-->
#### Testing
1. Add test cases to assert metrics with different
`elasticsearch.mapping.hints` values are grouped correctly

Author: isaacaflores2

.chloggen/es-exporter-ecs-hasher-exclude-mapping-hint.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. receiver/filelog)
+component: exporter/elasticsearch
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Update the ECS mode metrics data point hasher to exclude the `elasticsearch.mapping.hints` attribute
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [45887]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext: Excluding the `elasticsearch.mapping.hints` attribute will allow similar metric data points to be grouped together and indexed to the same document.
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

exporter/elasticsearchexporter/exporter_test.go

@@ -1931,6 +1931,61 @@ func TestExporterMetrics_Grouping(t *testing.T) {
 			})
 		}
 	})
+
+	t.Run("mapping hints excluded from grouping", func(t *testing.T) {
+		// Test that data points with different mapping hints are grouped together
+		// since elasticsearch.mapping.hints should be excluded from the hash.
+		for _, mode := range []string{"ecs", "otel"} {
+			t.Run(mode, func(t *testing.T) {
+				rec := newBulkRecorder()
+				server := newESTestServer(t, func(docs []itemRequest) ([]itemResponse, error) {
+					rec.Record(docs)
+					return itemsAllOK(docs)
+				})
+
+				testMetricsExporter := newTestMetricsExporter(t, server.URL, func(cfg *Config) {
+					cfg.Mapping.Mode = mode
+				})
+
+				metrics := pmetric.NewMetrics()
+				resource := metrics.ResourceMetrics().AppendEmpty()
+				scope := resource.ScopeMetrics().AppendEmpty()
+
+				// Metric with mapping hints
+				fooMetric := scope.Metrics().AppendEmpty()
+				fooMetric.SetName("metric.foo")
+				fooDp := fooMetric.SetEmptyGauge().DataPoints().AppendEmpty()
+				fooDp.SetDoubleValue(1.0)
+				hints := fooDp.Attributes().PutEmptySlice(elasticsearch.MappingHintsAttrKey)
+				hints.AppendEmpty().SetStr(string(elasticsearch.HintAggregateMetricDouble))
+
+				// Metric without mapping hints - should be grouped with the above
+				barMetric := scope.Metrics().AppendEmpty()
+				barMetric.SetName("metric.bar")
+				barDp := barMetric.SetEmptyGauge().DataPoints().AppendEmpty()
+				barDp.SetDoubleValue(2.0)
+
+				// Metric with different mapping hints - should still be grouped
+				bazMetric := scope.Metrics().AppendEmpty()
+				bazMetric.SetName("metric.baz")
+				bazDp := bazMetric.SetEmptyGauge().DataPoints().AppendEmpty()
+				bazDp.SetDoubleValue(3.0)
+				bazHints := bazDp.Attributes().PutEmptySlice(elasticsearch.MappingHintsAttrKey)
+				bazHints.AppendEmpty().SetStr(string(elasticsearch.HintDocCount))
+
+				mustSendMetrics(t, testMetricsExporter, metrics)
+
+				rec.WaitItems(1)
+				assert.Len(t, rec.Items(), 1)
+				// Sanity check that all metrics are included in a single document
+				// ECS mode uses short names (foo, bar, baz), OTel mode uses full names (metric.foo, etc.)
+				doc := string(rec.Items()[0].Document)
+				assert.Contains(t, doc, "foo")
+				assert.Contains(t, doc, "bar")
+				assert.Contains(t, doc, "baz")
+			})
+		}
+	})
 }
 
 func mapToDistinct(m map[string]any) attribute.Distinct {

exporter/elasticsearchexporter/internal/metricgroup/hasher.go

@@ -70,7 +70,7 @@ func (h *ECSDataPointHasher) HashKey() HashKey {
 	binary.LittleEndian.PutUint64(timestampBuf, uint64(h.dp.Timestamp()))
 	_, _ = hasher.Write(timestampBuf)
 
-	mapHashSortedExcludeReservedAttrs(hasher, merged)
+	mapHashSortedExcludeReservedAttrs(hasher, merged, elasticsearch.MappingHintsAttrKey)
 
 	return HashKey{
 		dpHash: hasher.Sum64(),