feat(fields): add instance domain (#9000)

# Which Problems Are Solved

Instance domains are only computed on read side. This can cause missing
domains if calls are executed shortly after a instance domain (or
instance) was added.

# How the Problems Are Solved

The instance domain is added to the fields table which is filled on
command side.

# Additional Changes

- added setup step to compute instance domains
- instance by host uses fields table instead of instance_domains table

# Additional Context

- part of https://github.com/zitadel/zitadel/issues/8999

cmd/setup/41.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 FillFieldsForInstanceDomains struct {
+	eventstore *eventstore.Eventstore
+}
+
+func (mig *FillFieldsForInstanceDomains) 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.InstanceDomainFields.Trigger(ctx); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (mig *FillFieldsForInstanceDomains) String() string {
+	return "41_fill_fields_for_instance_domains"
+}