Add validation to the response from license API

[thijsoo]

Context

• We want to make sure our license check shows a proper error if the response is not the expected result.

Summary

This PR can be summarized in the following changelog entry:

• Improves response validation of the Yoast license check. Props to aryanjasala.

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:

• Install this RC/PR on a site with a valid license and premium enabled.
• On a site with a valid license make sure the plans page still shows that you have a valid install. And make sure our morphology feature works.
• Install this PR/RC on a site that does not have a valid license but still has premium enabled.
• Make sure the morphology feature does not work and the plans page shows that your plan is not active.

For devs:

• open class-my-yoast-api-request.php and on line 70 between $response = $this->do_request( $this->url, $this->args ); and $response = $this->decode_response( $response ); add $response = '{"statusCode":200,"subscriptions": "ERROR","url": "ERROR"}';
• Make sure the license check fails gracefully by showing something is wrong in the alert center.
• Reset your transients with wp transient delete --all in the WP cli.
• Change the line to {"statusCode":404,"subscriptions": "ERROR","url": "ERROR"} and test again.
• Reset your transients with wp transient delete --all in the WP cli.
• Change the line to {"statusCode":404,"something":"random"} and test again.
• Reset your transients with wp transient delete --all in the WP cli.
• Change the line to RROR"} and test again.
• Be critical of other options and try those as well.

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 6227dd3809bccdf8057b56a581f2e6a2a45c2e0c

Details

• 7 of 8 (87.5%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.5%) to 53.407%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
inc/class-my-yoast-api-request.php	7	8	87.5%

Totals
Change from base Build 389a00f7adb7173a200dff217287813c8e4f3f52:	-0.5%
Covered Lines:	29987
Relevant Lines:	57022

---

💛 - Coveralls

[pls78]

CR && Acc: ✅