chore: introduce constant for operators

pkg/go/graph/graph_builder.go

@@ -91,15 +91,15 @@ func checkRewrite(graphBuilder *AuthorizationModelGraphBuilder, parentNode *Auth
 
  return
  case *openfgav1.Userset_Union:
- operator = "union"
+ operator = UnionOperator
  children = rw.Union.GetChild()
 
  case *openfgav1.Userset_Intersection:
- operator = "intersection"
+ operator = IntersectionOperator
  children = rw.Intersection.GetChild()
 
  case *openfgav1.Userset_Difference:
- operator = "exclusion"
+ operator = ExclusionOperator
  children = []*openfgav1.Userset{
  rw.Difference.GetBase(),
  rw.Difference.GetSubtract(),

pkg/go/graph/graph_node.go

@@ -12,13 +12,16 @@ const (
  SpecificTypeAndRelation NodeType = 1 // e.g. `group#viewer`
  OperatorNode NodeType = 2 // e.g. union
  SpecificTypeWildcard NodeType = 3 // e.g. `group:*`
+
+ UnionOperator = "union"
+ IntersectionOperator = "intersection"
+ ExclusionOperator = "exclusion"
 )
 
 type AuthorizationModelNode struct {
  graph.Node
 
- // custom attributes
- label string // e.g. `union`, for DOT
+ label string // e.g. "group#member", UnionOperator, IntersectionOperator, ExclusionOperator
  nodeType NodeType
  uniqueLabel string // e.g. `union:01J54ND7WHGAAJTGDMFWP4FZTR`
 }

pkg/go/graph/graph_test.go

@@ -218,11 +218,11 @@ func TestGetNodeTypes(t *testing.T) {
  }
 
  switch node.label {
- case "union":
+ case UnionOperator:
  unionNodes = append(unionNodes, node)
- case "intersection":
+ case IntersectionOperator:
  intersectionNodes = append(intersectionNodes, node)
- case "exclusion":
+ case ExclusionOperator:
  differenceNodes = append(differenceNodes, node)
  }
  }