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/permalink.go

@@ -0,0 +1,31 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+type Permalink struct {
+	PreviewPost *PreviewPost `json:"preview_post"`
+}
+
+type PreviewPost struct {
+	PostID             string      `json:"post_id"`
+	Post               *Post       `json:"post"`
+	TeamName           string      `json:"team_name"`
+	ChannelDisplayName string      `json:"channel_display_name"`
+	ChannelType        ChannelType `json:"channel_type"`
+	ChannelID          string      `json:"channel_id"`
+}
+
+func NewPreviewPost(post *Post, team *Team, channel *Channel) *PreviewPost {
+	if post == nil {
+		return nil
+	}
+	return &PreviewPost{
+		PostID:             post.Id,
+		Post:               post,
+		TeamName:           team.Name,
+		ChannelDisplayName: channel.DisplayName,
+		ChannelType:        channel.Type,
+		ChannelID:          channel.Id,
+	}
+}