v8.0 module release (#22975)

https://mattermost.atlassian.net/browse/MM-52079

```release-note
We upgrade the module version to 8.0. The new module path is github.com/mattermost-server/server/v8.
```


Co-authored-by: Doug Lauder <wiggin77@warpmail.net>

server/model/channel_data.go

@@ -0,0 +1,18 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+type ChannelData struct {
+	Channel *Channel       `json:"channel"`
+	Member  *ChannelMember `json:"member"`
+}
+
+func (o *ChannelData) Etag() string {
+	var mt int64 = 0
+	if o.Member != nil {
+		mt = o.Member.LastUpdateAt
+	}
+
+	return Etag(o.Channel.Id, o.Channel.UpdateAt, o.Channel.LastPostAt, mt)
+}