Implement a custom model validation provider for CAL

[Gelio]

Based on the investigation from #33, implement a model validation provider (a class that implements IValidationDescriptionProvider) for additional semantic CAL model validations.

Idea

There will be a new interface

interface ISemanticCALValidationRule {
  List<Diagnostic> validate(ComputationApplicationRelease application);
}

Each semantic rule (e.g. #27) will implement it.

The SemanticCALValidationDescriptionProvider will receive a list of ISemanticCALValidationRules and propagate the concatenated diagnostics returned by running each rule.

Resources

• the EMFValidationService used in Sirius Components to show the EMF model validation

  https://github.com/eclipse-sirius/sirius-components/blob/master/backend/sirius-web-emf/src/main/java/org/eclipse/sirius/web/emf/services/EMFValidationService.java

• how to get the objects inside of an EditingContext

  https://github.com/eclipse-sirius/sirius-components/blob/ab8097c6c3593f10fdd16f9212762624a3639ccc/backend/sirius-web-emf/src/main/java/org/eclipse/sirius/web/emf/services/EMFValidationService.java#L110-L112

  Note that this uses the EditingContext class, not the IEditingContext interface.

  That class just casts IEditingContext to EditingContext: https://github.com/eclipse-sirius/sirius-components/blob/ab8097c6c3593f10fdd16f9212762624a3639ccc/backend/sirius-web-emf/src/main/java/org/eclipse/sirius/web/emf/services/EMFValidationService.java#L54-L62

  We can probably do the same.

[Gelio]

I was wrong - implementing a new IValidationDescriptionProvider will not show the validations, because the code in SIrius Components handles only a single IValidationDescriptionProvider:

https://github.com/eclipse-sirius/sirius-components/blob/ab8097c6c3593f10fdd16f9212762624a3639ccc/backend/sirius-web-spring-collaborative-validation/src/main/java/org/eclipse/sirius/web/spring/collaborative/validation/ValidationEventProcessorFactory.java#L50-L52

As a result, I need to modify the code of the existing [ValidationDescriptionProvider](https://github.com/Gelio/CAL-web/blob/main/backend/sirius-web-services/src/main/java/org/eclipse/sirius/web/services/validation/ValidationDescriptionProvider.java to include running custom semantic validations.