MM-13664 Cache external link metadata when populating post metadata (#10128)

* MM-13664 Added LinkMetadata types

* MM-13664 Use LinkMetadata when populating post metadata

* Fix unused import

* Fix index name on SQLite

* Finish adding unit tests

* Address feedback

* Increase max length of URL column to 2048 characters

app/reaction.go

@@ -143,7 +143,7 @@ func (a *App) sendReactionEvent(event string, reaction *model.Reaction, post *mo
 	post.HasReactions = hasReactions
 	post.UpdateAt = model.GetMillis()
 
-	clientPost := a.PreparePostForClient(post)
+	clientPost := a.PreparePostForClient(post, false)
 
 	umessage := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_POST_EDITED, "", post.ChannelId, "", nil)
 	umessage.Add("post", clientPost.ToJson())