RUM-3175 fix: Fix race condition during consent change (pending → granted)

[ganeshnj]

What and why?

📦🐞 This PR fixes a race condition that occurs during the change of tracking consent from .pending to .granted. This issue could result in the loss of events recorded on the current thread right before the consent change.

How?

The fix involves synchronizing data migration on the context queue to prevent conflicts with ongoing "event write" operations. This change guarantees that all latest events are accurately migrated based on the updated consent state.

Review checklist

• Feature or bugfix MUST have appropriate tests (unit, integration)
• Make sure each commit and the PR mention the Issue number or JIRA reference
• Add CHANGELOG entry for user facing changes

[datadog-datadog-prod-us1]

Datadog Report

Branch report: ganeshnj/fix/consent-migration
Commit report: 817a0e1
Test service: dd-sdk-ios

✅ 0 Failed, 3473 Passed, 0 Skipped, 3m 35.42s Total Time
🔻 Test Sessions change in coverage: 2 decreased, 5 increased, 7 no change

🔻 Code Coverage Decreases vs Default Branch (2)

• test DatadogInternalTests tvOS 79.51% (-0.04%) - Details
• test DatadogRUMTests iOS 81.09% (-0.02%) - Details

[maxep]

The flush is a sync method:

/// Flushes asynchronous operations related to events write, context and message bus propagation in this instance of the SDK
/// with **blocking the caller thread** till their completion.

We should not block the user thread here, the flush method is mostly used for testing.
Instead, it might be sufficient to just publish the new consent before doing the migration. Or to call the migration from the context queue, also after publishing the new consent.

I would also be great to have a test case covering this, to prevent regression.

[ncreated]

(...) to call the migration from the context queue, also after publishing the new consent.

@maxep Fair call ✅. I continued this work fixing it in proposed way ☝️. It's not necessary to publish the consent before migration task as migration depends on the new consent value explicitly.

[maxep]

Nice, on target 🎯 😉

[ncreated]

/merge

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🚨 MergeQueue: This merge request is in error

mergequeue build completed successfully, but the github api returned an error while merging the pr.
It's probably because:

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Details

Error: PUT https://api.github.com/repos/DataDog/dd-sdk-ios/pulls/2063/merge: 405 Required status check "dd-gitlab/Sync GH Checks" is expected. []

FullStacktrace:
activity error (type: github.GithubService_MergePullRequest, scheduledEventID: 41, startedEventID: 42, identity: 1@github-worker-78dd5544fc-6gzkw@): PUT https://api.github.com/repos/DataDog/dd-sdk-ios/pulls/2063/merge: 405 Required status check "dd-gitlab/Sync GH Checks" is expected. [] (type: GitFailure, retryable: false): PUT https://api.github.com/repos/DataDog/dd-sdk-ios/pulls/2063/merge: 405 Required status check "dd-gitlab/Sync GH Checks" is expected. [] (type: ErrorResponse, retryable: true)

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[ncreated]

/merge

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[dd-devflow]

🚂 MergeQueue: pull request added to the queue

The median merge time in develop is 29m.

Use /merge -c to cancel this operation!