[5.0][Events] Custom fields event classes

[Fedik]

Summary of Changes

Event classes for Custom fields.

Affected events:

• onCustomFieldsGetTypes
• onCustomFieldsPrepareDom
• onCustomFieldsBeforePrepareField
• onCustomFieldsPrepareField
• onCustomFieldsAfterPrepareField

Testing Instructions

Use custom fields

Actual result BEFORE applying this Pull Request

Works

Expected result AFTER applying this Pull Request

Works

Link to documentations

Please select:

• Documentation link for docs.joomla.org: https://docs.joomla.org/Plugin/Events#Fields
• No documentation changes for docs.joomla.org needed
• Pull Request link for manual.joomla.org: New Event classes Manual#177
• No documentation changes for manual.joomla.org needed

[HLeithner]

Merging this as with code review and based on the other similar PRs, before beta1 to get enough feedback for final release.

Additionally we need a deprecation warning for plugins which extend the FieldsPlugin without the subscriber interface.

Suggestion, create a constructor function which test if $this is instance of SubscriberInterface.

[Fedik]

This is unnecessary, whole legacy listeners code should go, not only for FieldsPlugin.

[HLeithner]

yes but that means we have to call $y = $event->getY() anyway when we don't have references anymore. In this case maybe it make sense to not have (pseudo)references at the caller location at all and always run $x = $event->getX() for every reference/proxyArray we use now?

[Fedik]

You comented in wrong PR :)