docs(server-events): leave channel out for Subscribe with Google

[ste26054]

What

• docs/🧐 Analytics/server-events/server-events-attributes.md, the channel attribute: in_app now excludes Subscribe with Google. The channel key is absent for Subscribe with Google purchases, which carry is_swg: true.
• The in_app definition is split into short sentences.

Why

Purchasely/Purchasely-Backend#5011 gives Subscribe with Google subscriptions no channel. The user buys them on the publisher's website through Google, without the app. So they are neither in_app nor app2web (started in the app, paid on the web). Webhooks sent in_app for them before.

How to verify

• Read the channel row of the page. It matches PurchaseChannel.for in Purchasely/Purchasely-Backend#5011.

Notes

• Publish this together with Purchasely/Purchasely-Backend#5011. That PR waits for the mobile_application_id backfill on subscriptions to finish.
• Pre-PR review: Codex gpt-6-astra (Herdr reviewer) reviewed origin/v6.0..16107718 with the backend change. Fixed: the in_app definition had 24 words.

Greptile

Skipped: Markdown docs only (one table cell)

[greptile-apps]

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