ref(android): Support Nav3 for multi-Activity applications

[0xadam-brown]

📜 Description

PR allows separate SentryNavEffect instances to overlap during Activity or Fragment transitions without stale cleanup clobbering the active observer.**

Like all forms of state management around Android lifecycles, this code isn't exactly simple. To keep things manageable (and easy to update!), I've been careful to sequester all state management to the NavScopes file. The basic idea was simply to replace the IScopes instance BackStackObserver already talked to with a smarter version that could toggle between the shared underlying scope and a per-instance staged version, depending on whether the observer was associated with the incoming or outgoing SentryNavEffect.

That^^ let me keep updates to SentryNavEffect, BackStackObserver, etc. to a minimum, and it makes it easy to swap out our implementation in the future, should we ever hide our IScopes API behind a LocalSentrySpan-esque system (or any of a number of other possibilities) 🎉 .

See the NavScopes KDoc for more details, including some helpful diagrams.

💡 Motivation and Context

Lets us support multi-Activity or multi-Fragment apps, where each Activity / Fragment has its own SentryNavEffect <> NavDisplay pair. That setup is common, and without the changes here, spans and nav state would be incorrect for the initial destination in each newly-launched Activity.

That's worrisome, because Activity startup logic is a common source of bugs / crashes, so properly attributing Sentry data there is especially worthwhile.

addresses: JAVA-274

💚 How did you test it?

• Unit tests
• Had my clanker use the new Nav3 sample app tab introduced in this PR to verify that nav data was interleaved and garbled when switching between Activity <> SentryNavEffect pairs prior to this PR, and fixed after.

📝 Checklist

• I added GH Issue ID & Linear ID
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• I updated the wizard if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.
• Public API changes reviewed by another Mobile SDK team member or implemented according to the develop docs spec.

🔮 Next steps

• Update sentry-docs to match the updates here.

[sentry]

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
SDK Size	io.sentry.tests.size	8.60.0 (1)	release

⚙️ sentry-android Build Distribution Settings