Add ai free spark route

[vraja-pro]

Context

Summary

This PR can be summarized in the following changelog entry:

• Adds the route to save timestamp when user starts the AI generator trial.
• Refactor AI consent modal.

Relevant technical choices:

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• Use postman, thunder or any other tool to test apis.
• Create a POST request to http://wordpress.test/wp-json/yoast/v1/ai/free_sparks, replace http://wordpress.test with your test site.
• To the headers add X-WP-Nonce the value should be window.wpApiSettings.nonce in your site.
• Add Cookie to the header, (go to the application tab in the devtools, copy the Name, starting with "wordpress_logged_in...", add "=" and paste the value of that same line.
• Check you are getting the response: ""Free sparks successfully started."
• Go to the database, in the wp_options table, look for wpseo and in the value, search for ai_free_sparks_started_on.
• Check it has a string value for the timestamp.
• Smoke test consent modal when editing a post and on profile page. Make sure you are able to grant and revoke consent.

Relevant test scenarios

• Changes should be tested with the browser console open
• Changes should be tested on different posts/pages/taxonomies/custom post types/custom taxonomies
• Changes should be tested on different editors (Default Block/Gutenberg/Classic/Elementor/other)
• Changes should be tested on different browsers
• Changes should be tested on multisite

Test instructions for QA when the code is in the RC

• QA should use the same steps as above.

QA can test this PR by following these steps:

Impact check

This PR affects the following parts of the plugin, which may require extra testing:

UI changes

• This PR changes the UI in the plugin. I have added the 'UI change' label to this PR.

Other environments

• This PR also affects Shopify. I have added a changelog entry starting with [shopify-seo], added test instructions for Shopify and attached the Shopify label to this PR.

Documentation

• I have written documentation for this change. For example, comments in the Relevant technical choices, comments in the code, documentation on Confluence / shared Google Drive / Yoast developer portal, or other.

Quality assurance

• I have tested this code to the best of my abilities.
• During testing, I had activated all plugins that Yoast SEO provides integrations for.
• I have added unit tests to verify the code works as intended.
• If any part of the code is behind a feature flag, my test instructions also cover cases where the feature flag is switched off.
• I have written this PR in accordance with my team's definition of done.
• I have checked that the base branch is correctly set.

Innovation

• No innovation project is applicable for this PR.
• This PR falls under an innovation project. I have attached the innovation label.
• I have added my hours to the WBSO document.

Fixes #

[coveralls]

Pull Request Test Coverage Report for Build 7bad6d520b241a3dfc62247bef9bf3df616483ba

Details

• 17 of 43 (39.53%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.001%) to 52.05%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
inc/options/class-wpseo-option-wpseo.php	0	1	0.0%
packages/js/src/ai-generator/components/modal-content.js	0	1	0.0%
src/ai-free-sparks/user-interface/free-sparks-route.php	0	24	0.0%

Totals
Change from base Build b3a2d8dc0288da9b80e027452e34acad80e210a4:	-0.001%
Covered Lines:	29925
Relevant Lines:	58613

---

💛 - Coveralls

[vraja-pro]

Missing tests for src/ai-free-sparks/user-interface/free-sparks-route.php, will be added in a different PR.

[vraja-pro]

CR & AC ✅