Feature Request: Add Support for Association Names and Association Classes Description

[ArmenSl]

Currently, the Apollon editor lacks support for defining association names and association classes, which are fundamental concepts in UML modeling. Adding these features would enhance the functionality and align the tool more closely with UML standards.

Proposed Solution

Association Names:
Allow users to define and display names on associations.
The name should be editable and positioned near the association line.
Support for additional attributes such as multiplicity or directionality indicators could be considered.

Association Classes:
Enable linking a class to an association, representing it as a dotted line connecting the class and the association.
The class should display attributes, operations, and other UML elements as part of its definition.