This article aims at simplifying sending proactive events to an Alexa Skill from an external Java process.
Based on the video, From Zero to Hero, Part 13: Proactive Events Notifications by German Viscuso, and the Github project by Luca Rosellini written in NodeJS. I have created a Java client so that it is easy to send notifications from any Java/Kotlin-based backend or, for example, from any Android device.