Add component-id for HighlightsNewsletterCard

[georgerichmond]

What does this change?

Adds a data-modal-component-id attribute to the <a> tag in HighlightsNewsletterCard:

• data-modal-component-id — matches the signup modal's Ophan component.id (HighlightsNewsletterModal <identityName>)

The value is derived from the existing NEWSLETTER_SIGNUP_COMPONENT_ID.highlightsModal helper, so it is guaranteed to stay in sync with the events already sent to Ophan. Tests are updated to assert the attribute is present and correctly valued.

Why?

Heatphan needs a DOM hook on the Highlights card to display modal-open and subscribe counts as a badge on the front. It listens for Ophan EXPAND and SUBSCRIBE events, using the component.id to identify which element to update — so the <a> tag needs a matching attribute for Heatphan to hook into.

The card and its modal have separate component IDs (split in #16258, because EXPAND fires twice — once when the modal opens, and again when the captcha loads — and a shared ID made them indistinguishable). data-modal-component-id points to the modal's ID, which is the one associated with the EXPAND (modal-open) and SUBSCRIBE events Heatphan cares about.

Screenshots

No visual change.

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[github-actions]

Deploy build 2038 of dotcom:ab-testing to CODE

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[github-actions]

Deploy build 28691 of dotcom:rendering-all to CODE

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From guardian/actions-riff-raff.