MM-10649: soften Channels.ExtraUpdateAt deprecation (#8843)

The previous complete removal of this field resulted in an
incompatibility with 4.x servers that could not handle the now null
column field.

Instead, ensure this field is at least always set to 0, with a plan to
remove it altogether in a future release.

model/channel.go

@@ -44,6 +44,7 @@ type Channel struct {
 	Purpose       string `json:"purpose"`
 	LastPostAt    int64  `json:"last_post_at"`
 	TotalMsgCount int64  `json:"total_msg_count"`
+	ExtraUpdateAt int64  `json:"extra_update_at"`
 	CreatorId     string `json:"creator_id"`
 }
 
@@ -132,6 +133,7 @@ func (o *Channel) PreSave() {
 
 	o.CreateAt = GetMillis()
 	o.UpdateAt = o.CreateAt
+	o.ExtraUpdateAt = 0
 }
 
 func (o *Channel) PreUpdate() {

store/storetest/channel_store.go

@@ -713,6 +713,9 @@ func testChannelMemberStore(t *testing.T, ss store.Store) {
 	c1.Type = model.CHANNEL_OPEN
 	c1 = *store.Must(ss.Channel().Save(&c1, -1)).(*model.Channel)
 
+	c1t1 := (<-ss.Channel().Get(c1.Id, false)).Data.(*model.Channel)
+	assert.EqualValues(t, 0, c1t1.ExtraUpdateAt, "ExtraUpdateAt should be 0")
+
 	u1 := model.User{}
 	u1.Email = model.NewId()
 	u1.Nickname = model.NewId()
@@ -737,6 +740,9 @@ func testChannelMemberStore(t *testing.T, ss store.Store) {
 	o2.NotifyProps = model.GetDefaultChannelNotifyProps()
 	store.Must(ss.Channel().SaveMember(&o2))
 
+	c1t2 := (<-ss.Channel().Get(c1.Id, false)).Data.(*model.Channel)
+	assert.EqualValues(t, 0, c1t2.ExtraUpdateAt, "ExtraUpdateAt should be 0")
+
 	count := (<-ss.Channel().GetMemberCount(o1.ChannelId, true)).Data.(int64)
 	if count != 2 {
 		t.Fatal("should have saved 2 members")
@@ -767,6 +773,9 @@ func testChannelMemberStore(t *testing.T, ss store.Store) {
 		t.Fatal("should have removed 1 member")
 	}
 
+	c1t3 := (<-ss.Channel().Get(c1.Id, false)).Data.(*model.Channel)
+	assert.EqualValues(t, 0, c1t3.ExtraUpdateAt, "ExtraUpdateAt should be 0")
+
 	member := (<-ss.Channel().GetMember(o1.ChannelId, o1.UserId)).Data.(*model.ChannelMember)
 	if member.ChannelId != o1.ChannelId {
 		t.Fatal("should have go member")
@@ -775,6 +784,9 @@ func testChannelMemberStore(t *testing.T, ss store.Store) {
 	if err := (<-ss.Channel().SaveMember(&o1)).Err; err == nil {
 		t.Fatal("Should have been a duplicate")
 	}
+
+	c1t4 := (<-ss.Channel().Get(c1.Id, false)).Data.(*model.Channel)
+	assert.EqualValues(t, 0, c1t4.ExtraUpdateAt, "ExtraUpdateAt should be 0")
 }
 
 func testChannelDeleteMemberStore(t *testing.T, ss store.Store) {
@@ -785,6 +797,9 @@ func testChannelDeleteMemberStore(t *testing.T, ss store.Store) {
 	c1.Type = model.CHANNEL_OPEN
 	c1 = *store.Must(ss.Channel().Save(&c1, -1)).(*model.Channel)
 
+	c1t1 := (<-ss.Channel().Get(c1.Id, false)).Data.(*model.Channel)
+	assert.EqualValues(t, 0, c1t1.ExtraUpdateAt, "ExtraUpdateAt should be 0")
+
 	u1 := model.User{}
 	u1.Email = model.NewId()
 	u1.Nickname = model.NewId()
@@ -809,6 +824,9 @@ func testChannelDeleteMemberStore(t *testing.T, ss store.Store) {
 	o2.NotifyProps = model.GetDefaultChannelNotifyProps()
 	store.Must(ss.Channel().SaveMember(&o2))
 
+	c1t2 := (<-ss.Channel().Get(c1.Id, false)).Data.(*model.Channel)
+	assert.EqualValues(t, 0, c1t2.ExtraUpdateAt, "ExtraUpdateAt should be 0")
+
 	count := (<-ss.Channel().GetMemberCount(o1.ChannelId, false)).Data.(int64)
 	if count != 2 {
 		t.Fatal("should have saved 2 members")