Emit warning when stripe-notify header is present in response

[xavdid]

Why?

We've noticed a trend where users (and their agents) will sometimes reach for suboptimal API endpoints/methods because of outdated information. For example, using /v1/accounts when /v2/core/accounts is available and has a superset of the functionality from v1.

In an effort to help steer users towards best practices, we're introducing a new header to provide feedback during the development process. The SDK is responsible for surfacing this header, if present.

Once enabled internally, the header will be returned by the server for:

• all testmode calls
• livemode calls made by an agent

We may tweak that going forwards. But no matter the conditions, the SDKs will act as a thin pipe.

What?

• Emit warning when we see the Stripe-Notice header in a response. Note this is the first warning we're emitting in this SDK, so make sure it's the correct way to do that!
• add tests

See Also

• https://go/agent-steering
• DEVSDK-2430

[jar-stripe]

The code looks good; the changes I'd like to see are at the PR level, specifically, can you attach results of a test run that shows what an agent will see when this is hit? Even better if we can verify that the agent will see that on the correct output channel.