download
fun downloadApp(appId: Int, depotId: Int, installPath: String, stagingPath: String, branch: String = "public", maxDownloads: Int = 8, onDownloadProgress: (Float) -> Unit? = null, parentScope: CoroutineScope = defaultScope): Deferred<Boolean>
Kotlin coroutines version
fun downloadApp(appId: Int, depotId: Int, installPath: String, stagingPath: String, branch: String = "public", maxDownloads: Int = 8, progressCallback: ProgressCallback? = null): CompletableFuture<Boolean>
Java-friendly version that returns a CompletableFuture