Privacy: Surface email-send failures when initiating a personal data request

[irozum]

What: When an admin adds a new personal data export/erasure request with "send confirmation email" checked, _wp_personal_data_handle_actions() calls wp_send_user_request() but discards its return value, then unconditionally shows "Confirmation request initiated successfully." Since wp_send_user_request() returns a WP_Error on mail failure, the admin gets a false success message even when the confirmation email never went out — leaving the request stuck pending with no obvious explanation.

Fix: Check the return value of wp_send_user_request() and, if it's a WP_Error, surface the actual error message via add_settings_error() (type error) instead of the canned success string — mirroring the existing pattern used a few lines above for wp_create_user_request() failures and in _wp_privacy_resend_request()'s retry path.

Tests: Added tests/phpunit/tests/privacy/wpPersonalDataHandleActions.php, covering both the failure path (forcing wp_mail() to fail via the wp_mail_from filter, per the existing pattern in Tests_User_wpSendUserRequest) and the existing success path as a regression guard.

Trac ticket: https://core.trac.wordpress.org/ticket/54442

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Sonnet 5
Used for: Implementation, tests, and PR description. Reviewed by Igor Rozum.

---

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

Core Committers: Use this line as a base for the props when committing in SVN:

Props irozum.

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[github-actions]

Test using WordPress Playground

The changes in this pull request can previewed and tested using a WordPress Playground instance.

WordPress Playground is an experimental project that creates a full WordPress instance entirely within the browser.

Some things to be aware of

• All changes will be lost when closing a tab with a Playground instance.
• All changes will be lost when refreshing the page.
• A fresh instance is created each time the link below is clicked.
• Every time this pull request is updated, a new ZIP file containing all changes is created. If changes are not reflected in the Playground instance,
  it's possible that the most recent build failed, or has not completed. Check the list of workflow runs to be sure.

For more details about these limitations and more, check out the Limitations page in the WordPress Playground documentation.

Test this pull request with WordPress Playground.