How to create a pop up in Sonarqube

Hi everyone for this plugin I am building I want to add a pop up if the user inputs incorrect values such as a bad API key. How would I go about doing this?
What I am thinking is just a pop up anywhere on the screen kinda like what SQ has for the local SonarQube instance, where the warning message is saying that an internal database is only for development purposes. I would like to have something similar but for my own messages are there anyways to add this functionality.