Fix application_store_snapshot event not showing up in Tracks

[jaclync]

Part of #10574

Why

Even though we implemented the Tracks event application_store_snapshot in #10484, we didn't see any events in Tracks after a day of release.

After a deeper look, I found a silent validation error on the event properties because the property name can only contain alpha characters and underscores while the payment gateway properties have -: Custom properties dictionary keys must contain alpha characters and underscores only.

Validation errors like this aren’t logged to the console at all, and were missed during development/review. I'm also looking into the validation error logging issue in Automattic/Automattic-Tracks-iOS#262.

How

The event properties are fixed by replacing - with _ in payment gateway event properties in the snapshot event.

Testing instructions

• Reinstall the app, or log in to a store whose snapshot hasn't been tracked
• Log in and connect to a store --> shortly after entering the site, an event is logged in the console 🔵 Tracked application_store_snapshot AND it should also get sent in the Tracks POST request after a bit. You can check the Tracks POST request body in the Menu tab > Settings > Launch Wormholy Debug, and search for tracks/record POST requests and find application_store_snapshot in the request body

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• @jaclync make sure the event shows up in Tracks

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[jaclync]

Hi @spencertransier 👋 just a heads up that it'd be great if this PR can be merged to the release 15.1 branch when it's ready for the beta build.

[wpmobilebot]

You can test the changes from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr10575-00ff80f on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[ThomazFB]

Looks good!

[spencertransier]

@jaclync This fix is in the 15.1.0.2 build that'll be available in TestFlight shortly.

[jaclync]

Thanks for the review @ThomazFB & release updates @spencertransier! 🙏