perf(import): optimize search for domains claimed by other organizations (#8200)

# Which Problems Are Solved

Improve the performance of human imports by optimizing the query that
finds domains claimed by other organizations.

# How the Problems Are Solved

Use the fields search table introduced in
https://github.com/zitadel/zitadel/pull/8191 by storing each
organization domain as Object ID and the verified status as field value.

# Additional Changes

- Feature flag for this optimization

# Additional Context

- Performance improvements for import are evaluated and acted upon
internally at the moment

---------

Co-authored-by: adlerhurst <silvan.reusser@gmail.com>

cmd/setup/30.go

@@ -0,0 +1,42 @@
+package setup
+
+import (
+	"context"
+
+	"github.com/zitadel/zitadel/internal/api/authz"
+	"github.com/zitadel/zitadel/internal/eventstore"
+	"github.com/zitadel/zitadel/internal/query/projection"
+	"github.com/zitadel/zitadel/internal/repository/instance"
+)
+
+type FillFieldsForOrgDomainVerified struct {
+	eventstore *eventstore.Eventstore
+}
+
+func (mig *FillFieldsForOrgDomainVerified) Execute(ctx context.Context, _ eventstore.Event) error {
+	instances, err := mig.eventstore.InstanceIDs(
+		ctx,
+		0,
+		true,
+		eventstore.NewSearchQueryBuilder(eventstore.ColumnsInstanceIDs).
+			OrderDesc().
+			AddQuery().
+			AggregateTypes("instance").
+			EventTypes(instance.InstanceAddedEventType).
+			Builder(),
+	)
+	if err != nil {
+		return err
+	}
+	for _, instance := range instances {
+		ctx := authz.WithInstanceID(ctx, instance)
+		if err := projection.OrgDomainVerifiedFields.Trigger(ctx); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (mig *FillFieldsForOrgDomainVerified) String() string {
+	return "30_fill_fields_for_org_domain_verified"
+}