chore: add relationship index storing caveat to migrations

internal/datastore/crdb/migrations/zz_migration.0007_add_relation_index_storing_caveat.go

@@ -0,0 +1,27 @@
+package migrations
+
+import (
+	"context"
+
+	"github.com/jackc/pgx/v5"
+)
+
+const (
+	addRelationshipIndexStoringCaveatQuery = `
+		CREATE INDEX idx_relationship_caveat_storing ON relation_tuple (namespace, relation, object_id, userset_relation) STORING (caveat_name, caveat_context);
+	`
+)
+
+func init() {
+	err := CRDBMigrations.Register("add-relationship-index-storing-caveat", "add-relationship-counters-table", addRelationshipIndexStoringCaveat, noAtomicMigration)
+	if err != nil {
+		panic("failed to register migration: " + err.Error())
+	}
+}
+
+func addRelationshipIndexStoringCaveat(ctx context.Context, conn *pgx.Conn) error {
+	if _, err := conn.Exec(ctx, addRelationshipIndexStoringCaveatQuery); err != nil {
+		return err
+	}
+	return nil
+}