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/post_metadata.go

@@ -0,0 +1,86 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+type PostMetadata struct {
+	// Embeds holds information required to render content embedded in the post. This includes the OpenGraph metadata
+	// for links in the post.
+	Embeds []*PostEmbed `json:"embeds,omitempty"`
+
+	// Emojis holds all custom emojis used in the post or used in reaction to the post.
+	Emojis []*Emoji `json:"emojis,omitempty"`
+
+	// Files holds information about the file attachments on the post.
+	Files []*FileInfo `json:"files,omitempty"`
+
+	// Images holds the dimensions of all external images in the post as a map of the image URL to its dimensions.
+	// This includes image embeds (when the message contains a plaintext link to an image), Markdown images, images
+	// contained in the OpenGraph metadata, and images contained in message attachments. It does not contain
+	// the dimensions of any file attachments as those are stored in FileInfos.
+	Images map[string]*PostImage `json:"images,omitempty"`
+
+	// Reactions holds reactions made to the post.
+	Reactions []*Reaction `json:"reactions,omitempty"`
+
+	// Priority holds info about priority settings for the post.
+	Priority *PostPriority `json:"priority,omitempty"`
+
+	// Acknowledgements holds acknowledgements made by users to the post
+	Acknowledgements []*PostAcknowledgement `json:"acknowledgements,omitempty"`
+}
+
+type PostImage struct {
+	Width  int `json:"width"`
+	Height int `json:"height"`
+
+	// Format is the name of the image format as used by image/go such as "png", "gif", or "jpeg".
+	Format string `json:"format"`
+
+	// FrameCount stores the number of frames in this image, if it is an animated gif. It will be 0 for other formats.
+	FrameCount int `json:"frame_count"`
+}
+
+// Copy does a deep copy
+func (p *PostMetadata) Copy() *PostMetadata {
+	embedsCopy := make([]*PostEmbed, len(p.Embeds))
+	copy(embedsCopy, p.Embeds)
+
+	emojisCopy := make([]*Emoji, len(p.Emojis))
+	copy(emojisCopy, p.Emojis)
+
+	filesCopy := make([]*FileInfo, len(p.Files))
+	copy(filesCopy, p.Files)
+
+	imagesCopy := map[string]*PostImage{}
+	for k, v := range p.Images {
+		imagesCopy[k] = v
+	}
+
+	reactionsCopy := make([]*Reaction, len(p.Reactions))
+	copy(reactionsCopy, p.Reactions)
+
+	acknowledgementsCopy := make([]*PostAcknowledgement, len(p.Acknowledgements))
+	copy(acknowledgementsCopy, p.Acknowledgements)
+
+	var postPriorityCopy *PostPriority
+	if p.Priority != nil {
+		postPriorityCopy = &PostPriority{
+			Priority:                p.Priority.Priority,
+			RequestedAck:            p.Priority.RequestedAck,
+			PersistentNotifications: p.Priority.PersistentNotifications,
+			PostId:                  p.Priority.PostId,
+			ChannelId:               p.Priority.ChannelId,
+		}
+	}
+
+	return &PostMetadata{
+		Embeds:           embedsCopy,
+		Emojis:           emojisCopy,
+		Files:            filesCopy,
+		Images:           imagesCopy,
+		Reactions:        reactionsCopy,
+		Priority:         postPriorityCopy,
+		Acknowledgements: acknowledgementsCopy,
+	}
+}