feat: add prompt_title to the modal checkout data events

[laurelfulford]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

This PR, along with Automattic/newspack-plugin#4377 and Automattic/newspack-popups#1508, add the prompt_title to the GA4 data captured by the modal checkout when it's triggered from a campaign prompt, based on feedback.

See NPPM-2486.

How to test the changes in this Pull Request:

1. Apply this PR, and feat: include prompt_title with newspack_popup_id for data events newspack-plugin#4377 and feat: make prompt_title available to modal checkout data events  newspack-popups#1508
2. Set up a few products so you have at least one simple product and one product with variations.
3. Set up donations
4. Set up a few different campaigns, both inline and overlay. Add checkout button blocks and Donation blocks to your campaigns. For the variable product, set it up so the reader can pick the product variation as part of the checkout.
5. Using GA4, an extension like this, or by console logging something like console.log( 'Event Info:', eventName, filteredPayload ); before this line, go through some different checkout interactions with the prompts and make sure you confirm all the different events include the prompt_title:

With the Donate Block:

1. When you click 'Donate Now' confirm both the opened and loaded events include the prompt_title and it matches your prompt
2. When you enter your information and click 'Continue', confirm the continue event includes the prompt_title and it matches your prompt
3. When you click 'Edit Billing Information', confirm the back event includes the prompt_title and it matches your prompt
4. Back on the second screen, when you click 'Complete Transaction', confirm both the form_submission and form_submission_success messages include the prompt_title.
5. Repeat step a) and then close the modal checkout; confirm the dismissed event includes the prompt_title.

With the Checkout Button block

1. When you click the Checkout Button, confirm both the opened and loaded events include the prompt_title and it matches your prompt
2. When you enter your information and click 'Continue', confirm the continue event includes the prompt_title and it matches your prompt
3. When you click 'Edit Billing Information', confirm the back event includes the prompt_title and it matches your prompt
4. Back on the second screen, when you click 'Complete Transaction', confirm both the form_submission and form_submission_success messages include the prompt_title.
5. Repeat step a) and then close the modal checkout; confirm the dismissed event includes the prompt_title.

With the Checkout Button block with Variations

1. When you click the Checkout Button, confirm the variations modal opens and the opened_variations includes the prompt_title
2. When you pick a variation and click 'Purchase', confirm the opened and loaded events includes the prompt_title
3. Complete the transaction, and confirm both the form_submission and form_submission_success messages include the prompt_title.

With a standard Checkout/Donate Block

1. Just in case, test out a Checkout Button Block or Donate block in a regular post/page (not in a campaign) and double-check that what's being tracked looks okay. The full list of standard modal checkout GA4 events are here.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[dkoo]

All works as described!

[laurelfulford]

Thanks @dkoo! 🙌

[github-actions]

Hey @laurelfulford, good job getting this PR merged! 🎉

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