You can run it locally on your machine just by cloning the repo and running with gradle. Here's a list of the API endpoints:
// Users
GET("/users", userHandler::listUsersView)
GET("/api/users", userHandler::listUsersApi)
GET("/api/users/{login}", userHandler::getUserApi)
POST("/api/users", userHandler::createUserApi)
GET("/sse/users", userHandler::createUserSse)
// Messages
GET("/messages", messageHandler::listMessagesView)
GET("/api/messages", messageHandler::listMessagesApi)
GET("/api/messages/{id}", messageHandler::getMessageApi)
POST("/api/messages", messageHandler::createMessageApi)
GET("/sse/messages", messageHandler::createMessageSse)
// Configuration
GET("/conf", userHandler::conf)