Use mattermost v5 module (#1192)

vendor/github.com/mattermost/mattermost-server/v5/model/post_metadata.go

@@ -0,0 +1,45 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+import (
+	"encoding/json"
+)
+
+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 diemsnions.
+	// 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"`
+}
+
+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"`
+}
+
+func (o *PostImage) ToJson() string {
+	b, _ := json.Marshal(o)
+	return string(b)
+}