PLT-7705: API to get data retention policy. (#7539)

* PLT-7705: API to get data retention policy.

* Fix review comments.

einterfaces/data_retention.go

@@ -0,0 +1,12 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package einterfaces
+
+import (
+	"github.com/mattermost/mattermost-server/model"
+)
+
+type DataRetentionInterface interface {
+	GetPolicy() (*model.DataRetentionPolicy, *model.AppError)
+}

einterfaces/jobs/data_retention.go

@@ -7,7 +7,7 @@ import (
 	"github.com/mattermost/mattermost-server/model"
 )
 
-type DataRetentionInterface interface {
+type DataRetentionJobInterface interface {
 	MakeWorker() model.Worker
 	MakeScheduler() model.Scheduler
 }