Edge configuration for an ArcadeDB relationship declared in an arcade do … end
block. The %AshArcadic.Edge{} struct is the target of the edge DSL entity;
AshArcadic.Changes.{CreateEdge,DestroyEdge} read it by name.
multiple? selects the write primitive: false (default) → idempotent MERGE
(one edge per endpoint-pair + label); true → CREATE (parallel edges).