APIv4 DELETE /users/{user_id}/posts/{post_id}/reactions/name (#6117)

* APIv4 DELETE /users/{user_id}/posts/{post_id}/reactions/name

* updated v3 deleteReaction endpoint

* update parameter of app.DeleteReactionForPost()

* update utils.IsValidAlphaNum, add utils.IsValidAlphaNumHyphenUnderscore, and add related tests

model/reaction.go

@@ -60,7 +60,7 @@ func (o *Reaction) IsValid() *AppError {
 		return NewLocAppError("Reaction.IsValid", "model.reaction.is_valid.post_id.app_error", nil, "post_id="+o.PostId)
 	}
 
-	if len(o.EmojiName) == 0 || len(o.EmojiName) > 64 {
+	if len(o.EmojiName) == 0 || len(o.EmojiName) > 64 || !IsValidAlphaNumHyphenUnderscore(o.EmojiName, false) {
 		return NewLocAppError("Reaction.IsValid", "model.reaction.is_valid.emoji_name.app_error", nil, "emoji_name="+o.EmojiName)
 	}