Use string template for URL.

app/src/main/java/de/ccc/events/badge/card10/hatchery/HatcheryClient.kt

@@ -36,7 +36,7 @@ class HatcheryClient {
     fun getAppList(): List<App> {
         val client = OkHttpClient()
         val request = Request.Builder()
-            .url(HATCHERY_BASE_URL + "/eggs/list/json")
+            .url("$HATCHERY_BASE_URL/eggs/list/json")
             .build()
 
         val response: Response