Refactor filter event handling to a unified event with visitor pattern
to simplify the code, avoid future bugs and provide better test
coverage.
This commit shifts from using separate `filtered` and `filterRemoved`
events to a singular, more expressive `filterChanged` event. The new
approach emits a detailed payload that explicitly indicates the filter
action and the associated filter data. The event object unifies the way
the presentation layer reacts to the events.
Benefits with this approach include:
- Simplifying event listeners by reducing the number of events to
handle.
- Increasing code clarity and reduces potential for oversight by
providing explicit action details in the event payload.
- Offering extensibility for future actions without introducing new
events.
- Providing visitor pattern to handle different kind of events in easy
and robust manner without code repetition.
Other changes:
- Refactor components handling of events to follow DRY and KISS
principles better.
- Refactor `UserFilter.spec.ts` to:
- Make it easier to add new tests.
- Increase code coverage by running all event-based tests on the
current property.
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