v2.4.0: Prevents overwriting existing relations

Ensures that existing related entities are not overwritten when mapping form data to entities, specifically in to-many relationships.

It first checks if a component within the container represents a single identifier field. If it does, it attempts to find an existing entity using the identifier's value. Only if no such entity is found, a new entity is created. This prevents the creation of duplicate entities and ensures that existing relationships are maintained.