Jetpack AI: point upgrade buttons to checkout instead of product interstitial

[lhkowalski]

Fixes #39437.

Proposed changes:

• Update the checkout URL for Jetpack sites, to use the raw checkout link instead of the product interstitial
• Small refactor on how the checkout URL is built on WPCOM sites

Note: this will not change the behavior of the "Upgrade" button on the My Jetpack AI card, that will keep linking to the product interstitial

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

• Go to the block editor on a site with the free Jetpack AI plan
• Use the Jetpack AI until you reach the free limit of requests
  • alternativelly, sandbox the public-api domain and configure your 0-sandbox.php file to simulate this condition (see snippet below)
• We are going to check all upgrade buttons and links, to confirm they are redirecting the user to the checkout URL instead of the product interstitial page on My Jetpack
• Upgrade buttons and links to check:
  • on the sidebar
  • on the AI Assistant block
  • on the AI Extensions
  • on the image tools
    • featured (use the button on the Settings sidebar > Post tab)
    • general (use the button on the image block)
    • logo (use the button on the site logo block)
  • on the excerpt panel
• Click the links and confirm you land on the checkout for the Jetpack AI yearly plan
• When testing the last button/link, proceed with the checkout and confirm you are redirected back to your site, landing on the the Jetpack AI product page

Before	After

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Snippet to force a free plan on the 0-sandbox.php file:

add_filter( 'jetpack_ai_tier_licensed_quantity', function() { return 0; } );
add_filter( 'jetpack_ai_current_period_requests_count', function() { return 20; } );
add_filter( 'jetpack_ai_all_time_requests_count', function() { return 20; } ); // on the limit

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WordPress.com Simple site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin, and enable the update/jetpack-ai-change-upgrade-url branch.

• To test on Simple, run the following command on your sandbox:

  bin/jetpack-downloader test jetpack update/jetpack-ai-change-upgrade-url
  

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
• ✅ Add a "[Status]" label (In Progress, Needs Team Review, ...).
  
• ✅ Add testing instructions.
  
• ✅ Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

This comment will be updated as you work on your PR and make changes. If you think that some of those checks are not needed for your PR, please explain why you think so. Thanks for cooperation 🤖

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The e2e test report can be found here. Please note that it can take a few minutes after the e2e tests checks are complete for the report to be available.

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Follow this PR Review Process:

1. Ensure all required checks appearing at the bottom of this PR are passing.
2. Choose a review path based on your changes:
   • A. Team Review: add the "[Status] Needs Team Review" label
     • For most changes, including minor cross-team impacts.
     • Example: Updating a team-specific component or a small change to a shared library.
   • B. Crew Review: add the "[Status] Needs Review" label
     • For significant changes to core functionality.
     • Example: Major updates to a shared library or complex features.
   • C. Both: Start with Team, then request Crew
     • For complex changes or when you need extra confidence.
     • Example: Refactor affecting multiple systems.
3. Get at least one approval before merging.

Still unsure? Reach out in #jetpack-developers for guidance!

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Jetpack plugin:

The Jetpack plugin has different release cadences depending on the platform:

• WordPress.com Simple releases happen semi-continuously (PCYsg-Jjm-p2).
• WoA releases happen weekly.
• Releases to self-hosted sites happen monthly. The next release is scheduled for October 1, 2024 (scheduled code freeze on September 30, 2024).

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

[dhasilva]

LGTM