Support retention of locale on links

[christianwach]

Overview

Solves this issue on Lab.

Before

1. The method to generate URLs for WordPress could not accommodate plugins that alter the structure of the URL to encode locale information on the front-end.
2. Locale support on the front-end was implemented directly in the getUFLocale() method.

After

1. A filter enables the url() method to generate front-end URLs that contain locale information as defined by 3rd party plugins.
2. A filter enables the getUFLocale() method to support front-end locales as defined by 3rd party plugins.

Technical Details

Requires this PR on CiviCRM-WordPress.

[civibot]

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[christianwach]

Anyone able to explain the test failure? I can't figure out what's failed.

[colemanw]

Yea those messages are pretty unhelpful. Let's try again: retest this please

[kcristiano]

retest this please

Test failure looks "wrong"

[eileenmcnaughton]

@kcristiano the test problem is resolved - this appears to be a purely Wordpress PR so I'll wait on your merge-request

[mlutfy]

We've been running this in prod for a while now (2-4 weeks?) and works well.

We also have other sites running WPML, with Shane's patch (based on PR 289 in the WP repo, adapted to the new structure), and both play well together.

[eileenmcnaughton]

@colemanw if this is otherwise good we could probably change branch & merge to the rc since it probably will still switch base cleanly

[colemanw]

Merging per review/testing by @mlutfy

[christianwach]

Thanks 👍