🐛 move document_version to global context

It turns out that the View `_dd.document_version` is replaced by another
unrelated version in the backend. I wanted to duplicate this field so we
can keep the original in views.

Because unknown `_dd` fields are discarded from View events by the
backend, I chose to put it in the global context, similarly to #1757
(and other before).

packages/rum-core/src/domain/assembly.spec.ts

@@ -1,5 +1,11 @@
 import type { RelativeTime } from '@datadog/browser-core'
-import { ErrorSource, ONE_MINUTE, display } from '@datadog/browser-core'
+import {
+  updateExperimentalFeatures,
+  resetExperimentalFeatures,
+  ErrorSource,
+  ONE_MINUTE,
+  display,
+} from '@datadog/browser-core'
 import { createRumSessionManagerMock } from '../../test/mockRumSessionManager'
 import { createRawRumEvent } from '../../test/fixtures'
 import type { TestSetupBuilder } from '../../test/specHelper'
@@ -442,6 +448,10 @@ describe('rum assembly', () => {
   })
 
   describe('view context', () => {
+    afterEach(() => {
+      resetExperimentalFeatures()
+    })
+
     it('should be merged with event attributes', () => {
       const { lifeCycle } = setupBuilder.build()
       notifyRawRumEvent(lifeCycle, {
@@ -455,15 +465,18 @@ describe('rum assembly', () => {
       )
     })
 
-    it('should include the view document version in non-view events', () => {
+    it('should include the view document version in global context', () => {
+      updateExperimentalFeatures(['report_view_document_version'])
       const { lifeCycle } = setupBuilder.build()
       notifyRawRumEvent(lifeCycle, {
         rawRumEvent: createRawRumEvent(RumEventType.RESOURCE),
       })
-      expect(serverRumEvents[0]._dd).toEqual(
+      expect(serverRumEvents[0].context).toEqual(
         jasmine.objectContaining({
-          view: {
-            document_version: 42,
+          _dd: {
+            view: {
+              document_version: 42,
+            },
           },
         })
       )

packages/rum-core/src/domain/assembly.ts

@@ -1,5 +1,6 @@
 import type { Context, RawError, EventRateLimiter, User } from '@datadog/browser-core'
 import {
+  isExperimentalFeatureEnabled,
   combine,
   isEmptyObject,
   limitModification,
@@ -104,12 +105,6 @@ export function startRumAssembly(
             session: {
               plan: session.plan,
             },
-            view:
-              rawRumEvent.type === RumEventType.VIEW
-                ? undefined
-                : {
-                    document_version: viewContext.documentVersion,
-                  },
             browser_sdk_version: canUseEventBridge() ? __BUILD_ENV__SDK_VERSION__ : undefined,
           },
           application: {
@@ -146,6 +141,14 @@ export function startRumAssembly(
           ;(serverRumEvent.usr as Mutable<RumEvent['usr']>) = commonContext.user as User & Context
         }
 
+        if (isExperimentalFeatureEnabled('report_view_document_version')) {
+          serverRumEvent.context._dd = {
+            view: {
+              document_version: viewContext.documentVersion,
+            },
+          }
+        }
+
         if (shouldSend(serverRumEvent, configuration.beforeSend, domainContext, eventRateLimiters)) {
           if (isEmptyObject(serverRumEvent.context)) {
             delete serverRumEvent.context