Persist DomainBase.nsHosts VKeys to SQL (#541)

Persist nsHosts in Cloud SQL

Persist the VKey based nameserver hosts field of DomainBase in Cloud SQL with
foreign key constraints.

db/src/main/resources/sql/flyway/V22__update_ns_hosts.sql

@@ -0,0 +1,54 @@
+-- Copyright 2020 The Nomulus Authors. All Rights Reserved.
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+--     http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+
+create table "DomainHost" (
+   domain_repo_id text not null,
+    ns_host_v_keys text
+);
+
+create table "HostResource" (
+   repo_id text not null,
+    creation_client_id text,
+    creation_time timestamptz,
+    current_sponsor_client_id text,
+    deletion_time timestamptz,
+    last_epp_update_client_id text,
+    last_epp_update_time timestamptz,
+    statuses text[],
+    fully_qualified_host_name text,
+    last_superordinate_change timestamptz,
+    last_transfer_time timestamptz,
+    superordinate_domain bytea,
+    primary key (repo_id)
+);
+
+create table "HostResource_inetAddresses" (
+   host_resource_repo_id text not null,
+    inet_addresses bytea
+);
+
+alter table if exists "DomainHost"
+   add constraint FKfmi7bdink53swivs390m2btxg
+   foreign key (domain_repo_id)
+   references "Domain";
+
+alter table if exists "DomainHost"
+  add constraint FK_DomainHost_host_valid
+  foreign key (ns_host_v_keys)
+  references "HostResource";
+
+alter table if exists "HostResource_inetAddresses"
+   add constraint FK6unwhfkcu3oq6q347fxvpagv
+   foreign key (host_resource_repo_id)
+   references "HostResource";