Protect against 404s when wpBasePage is mixed case but page slug isn't

[christianwach]

Overview

Partial fix for this issue on Lab.

Before

WordPress shows a 404 when wpBasePage is saved in mixed-case (e.g. "CiviCRM") and no CiviCRM content is rendered.

After

WordPress does not show a 404 when wpBasePage is saved in mixed-case (e.g. "CiviCRM") and renders CiviCRM content as expected.

Technical Details

WordPress requires wpBasePage to be lowercase or else it won't find the Base Page. If I understand how $config->wpBasePage is read, then this PR should always force it to lowercase regardless of what is saved.

This is only a partial fix because it papers over a deeper issue, which is that ideally the $post->post_name value that is stored in wpBasePage should be replaced with a wpBasePageID setting that saves the $post->ID.

[civibot]

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[eileenmcnaughton]

Makes sense - I'll leave it to @kcristiano to merge

[agileware-justin]

Related bug report, https://lab.civicrm.org/dev/core/-/issues/2213

[agileware-justin]

Good to merge. Thanks @christianwach and @kcristiano