Helm Toolkit: util to return a list of unique hosts for endpoint

This PS adds a util to return a list of unique hosts for an endpoint,
with the fqdn value returned as the 1st item in the list.

Change-Id: Idaa63fad908f04a2d233e29092f6df30edd55bdb
Signed-off-by: Pete Birley <pete@port.direct>

helm-toolkit/templates/utils/_host_list.tpl

@@ -0,0 +1,46 @@
+{{/*
+Copyright 2017 The Openstack-Helm Authors.
+
+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.
+*/}}
+
+{{/*
+abstract: |
+  Returns a list of unique hosts for an endpoint, in yaml.
+values: |
+  endpoints:
+    cluster_domain_suffix: cluster.local
+    oslo_db:
+      hosts:
+        default: mariadb
+      host_fqdn_override:
+        default: mariadb
+usage: |
+  {{ tuple "oslo_db" "internal" . | include "helm-toolkit.utils.host_list" }}
+return: |
+  hosts:
+  - mariadb
+  - mariadb.default
+*/}}
+
+{{- define "helm-toolkit.utils.host_list" -}}
+{{- $type := index . 0 -}}
+{{- $endpoint := index . 1 -}}
+{{- $context := index . 2 -}}
+{{- $host_fqdn := tuple $type $endpoint $context | include "helm-toolkit.endpoints.hostname_fqdn_endpoint_lookup" }}
+{{- $host_namespaced := tuple $type $endpoint $context | include "helm-toolkit.endpoints.hostname_namespaced_endpoint_lookup" }}
+{{- $host_short := tuple $type $endpoint $context | include "helm-toolkit.endpoints.hostname_short_endpoint_lookup" }}
+{{/* It is important that the FQDN host is 1st in this list, to ensure other function can use the 1st element for cert gen CN etc */}}
+{{- $host_list := list $host_fqdn $host_namespaced $host_short | uniq }}
+{{- dict "hosts" $host_list | toYaml }}
+{{- end -}}