This change makes it easier for developers to customize what happens when users click images in binary image fields. It supports more flexible extensions of the web interface without changing the standard user experience.

allow override handler in extended widget.

Description of the issue/feature this PR addresses:

Current behavior before PR:

Desired behavior after PR is merged:




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The mail app now organizes attachment box actions in a dedicated internal model instead of keeping them in the display component. This makes the feature easier to maintain and helps support more reliable future improvements without changing the user experience.

Before this PR, attachment box event handlers where stored inside the attachment box component.
This PR move the handlers inside a dedicated model.

part of task-2579306