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/collection.go

@@ -0,0 +1,20 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+type CollectionMetadata struct {
+	Id             string `json:"id"`
+	TeamId         string `json:"team_id"`
+	CollectionType string `json:"collection_type"`
+	Name           string `json:"name"`
+	RelativeURL    string `json:"relative_url"`
+}
+
+type TopicMetadata struct {
+	Id             string `json:"id"`
+	TeamId         string `json:"team_id"`
+	TopicType      string `json:"topic_type"`
+	CollectionType string `json:"collection_type"`
+	CollectionId   string `json:"collection_id"`
+}