[5.2][Events] Use event classes for User plugins

[Fedik]

Pull Request for Issue # .

Summary of Changes

Update user plugins to use SubscriberInterface and an event classes.

Testing Instructions

Check following user plugins should work as before:

contactcreator
joomla
profile
terms
token

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#User
• [ ] No documentation changes for docs.joomla.org needed
• [x] Pull Request link for manual.joomla.org: https://github.com/joomla/Manual/pull/177
• [ ] No documentation changes for manual.joomla.org needed

References:

• https://github.com/joomla/joomla-cms/pull/41317

[richard67]

Drone failure is not related to this PR.

[HLeithner]

This pull request has been automatically rebased to 5.3-dev.