[5.x][RFC] CMSPlugin: Subscriber Registration Checker Interface

[Fedik]

Summary of Changes

Adding Subscriber Registration Checker. Interface that allows Plugins to be checked before listener registration.
This allows the plugin to be registered only wheen special conditions are met, eg: only for specific application.

Testing Instructions

Code review by maintainers.

Edit

joomla-cms/plugins/system/guidedtours/src/Extension/GuidedTours.php

Lines 124 to 126 in 98f3ecd

	public function onBeforeCompileHead()
	{
	$app = $this->getApplication();

And add dd('Works'); at top of this method.

Then open Administrator page: you should get message "works"
And then open Site page: the page should be opened as usual

Link to documentations

Please select:

• Documentation link for docs.joomla.org:
• No documentation changes for docs.joomla.org needed
• Pull Request link for manual.joomla.org: Info about new Subscriber Registration Checker Manual#272
• No documentation changes for manual.joomla.org needed