NEW Add extension points for getURL methods

[Cambis]

Description

• Add extension points to update the link url.

Manual testing steps

Issues

• Add extension points to Link::getURL() #368

Pull request checklist

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  • See picking the right version
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• This change is covered with tests (or tests aren't necessary for this change)
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• CI is green

[SimulatedPanda]

Given that this change is extremely low risk and provides a benefit to the CMS 5.4 release, I approve this change for inclusion in spite of the current change freeze for v5.4

[GuySartorelli]

Please set this extension hook in Link::getURL() directly instead and name it updateURL. Then in these subclasses make this change:

Suggested change

	$url = $this->Email ? sprintf('mailto:%s', $this->Email) : '';
	$this->extend('updateGetURL', $url);
	return $url;
	$this->beforeExtending('updateURL', function (string &$url) {
	$url = $this->Email ? sprintf('mailto:%s', $this->Email) : '';
	});
	return parent::getURL();

[GuySartorelli]

LGTM, thanks for taking the time.