[Adminhtml] add Events to Widget Grid

[Hanmac]

Description (*)

This adds some Events to the Adminhtml/Widget/Grid,
allowing it to add more Columns without the need to extend the Grid classes.

Example:

• you can add a Join to another table in the set_collection Event
• and then add Columns in the prepare_columns_after Event

Related Pull Requests

• see OpenMage/magento-lts#<issue_number>

Fixed Issues (if relevant)

• fixes OpenMage/magento-lts#<issue_number>

Manual testing scenarios (*)

1. ...
2. ...

Questions or comments

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All automated tests passed successfully (all builds are green)

[sreichel]

How about using $_eventPrefix to access specific grids?

For _afterLoadCollection and _prepareColums we have to change some code to call parent method (instead of return $this).

[Hanmac]

@sreichel Block doesn't have $_eventPrefix (yet)
it is only defined for Core_Model_Abstract

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud