[Discover][APM] Detect OTEL spans for doc viewer (elastic#224439)

## Summary

This PR modifies the Span doc viewer check to be better equipped for
dealing with unprocessed OTEL trace spans. If there is no
`processed.event` field, we can start assuming there'd be OTEL specific
fields to check. Here, we check for `kind` which *should* be present, so
any value determines this to be a trace span. In the absence of `kind`
being present and no `processed.event` field (just a `data_stream.type`
field, we can assume it is a span regardless.


## How to test

* Add the following to your `kibana.dev.yml` file:
```yaml
discover.experimental.enabledProfiles:
  - observability-traces-data-source-profile
  - observability-traces-transaction-document-profile
  - observability-traces-span-document-profile
```
* Set up a source of unprocessed OTEL data to feed into ES (Open
telemetry demo, etc)
* Set your space to Observability mode, and go to Discover.
* Query for `traces-*` and open any record for the document viewer
* The Span Overview tab should be visible.

Author: Bluefinger

src/platform/packages/shared/kbn-discover-utils/src/field_constants.ts

@@ -32,6 +32,7 @@ export const SPAN_TYPE_FIELD = 'span.type';
 export const SPAN_SUBTYPE_FIELD = 'span.subtype';
 export const SPAN_DESTINATION_SERVICE_RESOURCE_FIELD = 'span.destination.service.resource';
 export const PROCESSOR_EVENT_FIELD = 'processor.event';
+export const OTEL_SPAN_KIND = 'kind';
 
 export const LOG_FILE_PATH_FIELD = 'log.file.path';
 export const DATASTREAM_NAMESPACE_FIELD = 'data_stream.namespace';

src/platform/plugins/shared/discover/public/context_awareness/profile_providers/observability/traces_document_profile/span_document_profile/profile.test.ts

@@ -76,6 +76,44 @@ describe('spanDocumentProfileProvider', () => {
         })
       ).toEqual(RESOLUTION_MISMATCH);
     });
+
+    it('does not match records with the correct data stream type but the incorrect processor event', () => {
+      expect(
+        spanDocumentProfileProvider.resolve({
+          rootContext: getRootContext({ profileId }),
+          dataSourceContext: DATA_SOURCE_CONTEXT,
+          record: buildMockRecord('index', {
+            'data_stream.type': ['traces'],
+            'processor.event': ['other'],
+          }),
+        })
+      ).toEqual(RESOLUTION_MISMATCH);
+    });
+
+    it('matches records with the correct data stream type and any OTEL `kind` field', () => {
+      expect(
+        spanDocumentProfileProvider.resolve({
+          rootContext: getRootContext({ profileId }),
+          dataSourceContext: DATA_SOURCE_CONTEXT,
+          record: buildMockRecord('index', {
+            'data_stream.type': ['traces'],
+            kind: 'Internal',
+          }),
+        })
+      ).toEqual(RESOLUTION_MATCH);
+    });
+
+    it('defaults to matching records with the correct data stream type but no processor event field', () => {
+      expect(
+        spanDocumentProfileProvider.resolve({
+          rootContext: getRootContext({ profileId }),
+          dataSourceContext: DATA_SOURCE_CONTEXT,
+          record: buildMockRecord('index', {
+            'data_stream.type': ['traces'],
+          }),
+        })
+      ).toEqual(RESOLUTION_MATCH);
+    });
   });
 
   describe('when root profile is NOT observability', () => {

src/platform/plugins/shared/discover/public/context_awareness/profile_providers/observability/traces_document_profile/span_document_profile/profile.ts

@@ -8,7 +8,12 @@
  */
 
 import type { DataTableRecord } from '@kbn/discover-utils';
-import { DATASTREAM_TYPE_FIELD, getFieldValue, PROCESSOR_EVENT_FIELD } from '@kbn/discover-utils';
+import {
+  DATASTREAM_TYPE_FIELD,
+  getFieldValue,
+  OTEL_SPAN_KIND,
+  PROCESSOR_EVENT_FIELD,
+} from '@kbn/discover-utils';
 import { TRACES_PRODUCT_FEATURE_ID } from '../../../../../../common/constants';
 import type { DocumentProfileProvider } from '../../../../profiles';
 import { DocumentType, SolutionType } from '../../../../profiles';
@@ -65,5 +70,10 @@ const getIsSpanRecord = ({ record }: { record: DataTableRecord }) => {
 const isSpanDocument = (record: DataTableRecord) => {
   const dataStreamType = getFieldValue(record, DATASTREAM_TYPE_FIELD);
   const processorEvent = getFieldValue(record, PROCESSOR_EVENT_FIELD);
-  return dataStreamType === 'traces' && processorEvent === 'span';
+  const spanKind = getFieldValue(record, OTEL_SPAN_KIND);
+
+  const isApmSpan = processorEvent === 'span';
+  const isOtelSpan = spanKind != null || processorEvent == null;
+
+  return dataStreamType === 'traces' && (isApmSpan || isOtelSpan);
 };