Move source files from 'java' to 'kotlin' folder

app/src/main/kotlin/com/github/gotify/api/Api.kt

@@ -0,0 +1,21 @@
+package com.github.gotify.api
+
+import retrofit2.Call
+import java.io.IOException
+
+internal object Api {
+    @Throws(ApiException::class)
+    fun <T> execute(call: Call<T>): T {
+        try {
+            val response = call.execute()
+
+            if (response.isSuccessful) {
+                return response.body() ?: throw ApiException("null response", response)
+            } else {
+                throw ApiException(response)
+            }
+        } catch (e: IOException) {
+            throw ApiException(e)
+        }
+    }
+}