[DON-3492] Add accessibility label to BPKBannerAlert

[Jasper Sion (jaspersion05)]

Summary

Adds accessibilityLabel support for the custom icon in BpkBannerAlert, closing the gap identified by the parity audit — previously there was no way to set a custom content description for the icon separate from the banner's alertTypeContentDescription.

Changes

• Added a new optional trailing parameter iconContentDescription: String? = null to BpkBannerAlert and BpkBannerAlertImpl, threaded through to the icon's contentDescription.
• The icon's content description now resolves as iconContentDescription ?: alertTypeContentDescription, preserving existing behaviour when the new parameter isn't supplied.
• Documented the new parameter in docs/compose/BannerAlert/README.md with a usage example showing a custom icon paired with its own accessibility label.
• Added BpkBannerAlertAccessibilityTest.kt covering both the explicit iconContentDescription case and the fallback-to-alertTypeContentDescription case, following the existing BpkCellItemAccessibilityTest.kt convention.

Compatibility

Source- and binary-compatible. The new parameter is appended last and defaults to null. All existing call sites in this repo and in skyscanner-app (Origami, Wasabi) use named arguments only, so none are affected.

Verification

• New accessibility tests added and pass locally.
• No visual/behavioural change for existing callers, so no snapshot re-recording was needed.

Remember to include the following changes:

• README.md
• Tests
• Screenshotting code
• Adding a component? Remember to expose it in the main header/index if applicable

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[skyscanner-backpack-bot]

	Warnings
⚠️	One or more component files were updated, but the tests weren't updated. If your change is not covered by existing tests please add snapshot tests.
⚠️	One or more component files were updated, but the docs screenshots weren't updated. If the changes are visual or it is a new component please regenerate the screenshots via ./gradlew recordScreenshots.

Generated by 🚫 Danger Kotlin against a2c7415

[Copilot]

Pull request overview

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Adds support for a separate accessibility label for the icon in BpkBannerAlert, allowing custom icons to have their own contentDescription (with a fallback to alertTypeContentDescription).

Changes:

• Added optional iconContentDescription: String? = null to BpkBannerAlert and BpkBannerAlertImpl, used for the icon’s contentDescription with a fallback behavior.
• Updated BannerAlert Compose docs with a new usage example for a custom icon accessibility label.
• Added new Compose accessibility tests for explicit and fallback content descriptions.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
docs/compose/BannerAlert/README.md	Documents the new iconContentDescription parameter with an example.
backpack-compose/src/main/kotlin/net/skyscanner/backpack/compose/banneralert/BpkBannerAlert.kt	Exposes the new optional API parameter and threads it through.
backpack-compose/src/main/kotlin/net/skyscanner/backpack/compose/banneralert/internal/BpkBannerAlertImpl.kt	Applies iconContentDescription to the rendered icon with fallback logic.
backpack-compose/src/androidTest/kotlin/net/skyscanner/backpack/compose/banneralert/BpkBannerAlertAccessibilityTest.kt	Adds coverage for explicit icon description and fallback behavior.

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[skyscanner-backpack-bot]

	Warnings
⚠️	One or more component files were updated, but the tests weren't updated. If your change is not covered by existing tests please add snapshot tests.
⚠️	One or more component files were updated, but the docs screenshots weren't updated. If the changes are visual or it is a new component please regenerate the screenshots via ./gradlew recordScreenshots.

Generated by 🚫 Danger Kotlin against 424ccb0