Use mattermost v5 module (#1192)

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

@@ -0,0 +1,23 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package model
+
+const (
+	POST_EMBED_IMAGE              PostEmbedType = "image"
+	POST_EMBED_MESSAGE_ATTACHMENT PostEmbedType = "message_attachment"
+	POST_EMBED_OPENGRAPH          PostEmbedType = "opengraph"
+	POST_EMBED_LINK               PostEmbedType = "link"
+)
+
+type PostEmbedType string
+
+type PostEmbed struct {
+	Type PostEmbedType `json:"type"`
+
+	// The URL of the embedded content. Used for image and OpenGraph embeds.
+	URL string `json:"url,omitempty"`
+
+	// Any additional data for the embedded content. Only used for OpenGraph embeds.
+	Data interface{} `json:"data,omitempty"`
+}