Add autoclose dm config parameter (#7734)

* add autoclose dm config parameter

* update naming

model/config.go

@@ -204,6 +204,7 @@ type ServiceSettings struct {
 	EnableChannelViewedMessages              *bool
 	EnableUserStatuses                       *bool
 	ClusterLogTimeoutMilliseconds            *int
+	CloseUnusedDirectMessages                *bool
 }
 
 type ClusterSettings struct {
@@ -1376,6 +1377,10 @@ func (o *Config) SetDefaults() {
 		o.ServiceSettings.ClusterLogTimeoutMilliseconds = NewInt(2000)
 	}
 
+	if o.ServiceSettings.CloseUnusedDirectMessages == nil {
+		o.ServiceSettings.CloseUnusedDirectMessages = NewBool(false)
+	}
+
 	if o.ElasticsearchSettings.ConnectionUrl == nil {
 		o.ElasticsearchSettings.ConnectionUrl = NewString(ELASTICSEARCH_SETTINGS_DEFAULT_CONNECTION_URL)
 	}