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/audits.go

@@ -0,0 +1,14 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+type Audits []Audit
+
+func (o Audits) Etag() string {
+	if len(o) > 0 {
+		// the first in the list is always the most current
+		return Etag(o[0].CreateAt)
+	}
+	return ""
+}