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/emoji.go

@@ -34,7 +34,7 @@ func (emoji *Emoji) IsValid() *AppError {
 		return NewLocAppError("Emoji.IsValid", "model.emoji.user_id.app_error", nil, "")
 	}
 
-	if len(emoji.Name) == 0 || len(emoji.Name) > 64 {
+	if len(emoji.Name) == 0 || len(emoji.Name) > 64 || !IsValidAlphaNumHyphenUnderscore(emoji.Name, false) {
 		return NewLocAppError("Emoji.IsValid", "model.emoji.name.app_error", nil, "")
 	}