feat: add domainIdRef/domainIdSelector support to identity resources

apis/cluster/identity/v1alpha1/projectv3_extractor.go

@@ -0,0 +1,30 @@
+/*
+Copyright 2022 Upbound Inc.
+Copyright 2023 Jakob Schlagenhaufer
+Copyright 2025 Yannick Schlosser
+*/
+
+package v1alpha1
+
+import (
+	"github.com/crossplane/crossplane-runtime/v2/pkg/reference"
+	"github.com/crossplane/crossplane-runtime/v2/pkg/resource"
+)
+
+// ExtractDomainID returns the external name of a ProjectV3 only when it
+// represents a domain (isDomain: true). Referencing a regular project
+// yields an empty value, causing reference resolution to fail.
+func ExtractDomainID() reference.ExtractValueFn {
+	return func(mg resource.Managed) string {
+		p, ok := any(mg).(*ProjectV3)
+		if !ok {
+			return ""
+		}
+		isDomain := (p.Spec.ForProvider.IsDomain != nil && *p.Spec.ForProvider.IsDomain) ||
+			(p.Status.AtProvider.IsDomain != nil && *p.Status.AtProvider.IsDomain)
+		if !isDomain {
+			return ""
+		}
+		return reference.ExternalName()(mg)
+	}
+}