code: private void migrateTenantDefinition(String keyspace) {
          TenantDefinition tempTenantDef = new TenantDefinition();
          tempTenantDef.setName(keyspace);
          Tenant migratingTenant = new Tenant(tempTenantDef);
          DColumn col = DBService.instance(migratingTenant).getColumn("Applications", "_tenant", "Definition");
          if (col == null) {
              return;
          }
          m_logger.info("Migrating tenant definition from keyspace {}", keyspace);
          TenantDefinition migratingTenantDef = new TenantDefinition();
          try {
              migratingTenantDef.parse(UNode.parseJSON(col.getValue()));
          } catch (Exception e) {
              m_logger.warn("Couldn't parse tenant definition; skipping migration of keyspace: " + keyspace, e);
              return;
          }
          storeTenantDefinition(migratingTenantDef);
          DBTransaction dbTran = new DBTransaction(migratingTenant);
          dbTran.deleteRow("Applications", "_tenant");
          DBService.instance(migratingTenant).commit(dbTran);
      }
docs: Migrate legacy "_tenant" row, if it exists to the Tenants table.