PLT-7404 Return viewed at times in view channel API response (#7428)

* Return viewed at times in view channel API response

* Updated transaction to read and write once

* Remove transaction and only update if new value greater than older

model/channel_view_test.go

@@ -0,0 +1,38 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package model
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestChannelViewJson(t *testing.T) {
+	o := ChannelView{ChannelId: NewId(), PrevChannelId: NewId()}
+	json := o.ToJson()
+	ro := ChannelViewFromJson(strings.NewReader(json))
+
+	if o.ChannelId != ro.ChannelId {
+		t.Fatal("ChannelIdIds do not match")
+	}
+
+	if o.PrevChannelId != ro.PrevChannelId {
+		t.Fatal("PrevChannelIds do not match")
+	}
+}
+
+func TestChannelViewResponseJson(t *testing.T) {
+	id := NewId()
+	o := ChannelViewResponse{Status: "OK", LastViewedAtTimes: map[string]int64{id: 12345}}
+	json := o.ToJson()
+	ro := ChannelViewResponseFromJson(strings.NewReader(json))
+
+	if o.Status != ro.Status {
+		t.Fatal("ChannelIdIds do not match")
+	}
+
+	if o.LastViewedAtTimes[id] != ro.LastViewedAtTimes[id] {
+		t.Fatal("LastViewedAtTimes do not match")
+	}
+}