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

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

* Fix review comments.

model/data_retention_policy.go

@@ -0,0 +1,36 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package model
+
+import (
+	"encoding/json"
+	"io"
+)
+
+type DataRetentionPolicy struct {
+	MessageDeletionEnabled bool  `json:"message_deletion_enabled"`
+	FileDeletionEnabled    bool  `json:"file_deletion_enabled"`
+	MessageRetentionCutoff int64 `json:"message_retention_cutoff"`
+	FileRetentionCutoff    int64 `json:"file_retention_cutoff"`
+}
+
+func (me *DataRetentionPolicy) ToJson() string {
+	b, err := json.Marshal(me)
+	if err != nil {
+		return ""
+	} else {
+		return string(b)
+	}
+}
+
+func DataRetentionPolicyFromJson(data io.Reader) *DataRetentionPolicy {
+	decoder := json.NewDecoder(data)
+	var me DataRetentionPolicy
+	err := decoder.Decode(&me)
+	if err == nil {
+		return &me
+	} else {
+		return nil
+	}
+}