Convert the LoginClient to kotlin (#5479)

* Convert the result classes to kotlin

* Convert response and callback to kotlin

* Cleanup code-quality warnings before converting

* Converted the LoginClient to kotlin

* Updated the UserExtendedInfoClientTest to be kotlin, and live in the correct spot

app/src/test/kotlin/fr/free/nrw/commons/auth/login/UserExtendedInfoClientTest.kt

@@ -0,0 +1,78 @@
+package fr.free.nrw.commons.auth.login
+
+import android.net.Uri
+import com.google.gson.GsonBuilder
+import com.google.gson.stream.MalformedJsonException
+import fr.free.nrw.commons.MockWebServerTest
+import io.reactivex.observers.TestObserver
+import org.junit.Before
+import org.junit.Test
+import org.wikipedia.dataclient.WikiSite
+import org.wikipedia.dataclient.mwapi.MwQueryResponse
+import org.wikipedia.json.NamespaceTypeAdapter
+import org.wikipedia.json.PostProcessingTypeAdapter
+import org.wikipedia.json.UriTypeAdapter
+import org.wikipedia.json.WikiSiteTypeAdapter
+import org.wikipedia.page.Namespace
+import retrofit2.Retrofit
+import retrofit2.adapter.rxjava2.RxJava2CallAdapterFactory
+import retrofit2.converter.gson.GsonConverterFactory
+
+class UserExtendedInfoClientTest : MockWebServerTest() {
+    private var apiService: LoginInterface? = null
+    private val observer = TestObserver<MwQueryResponse>()
+    private val gson = GsonBuilder()
+        .registerTypeHierarchyAdapter(Uri::class.java, UriTypeAdapter().nullSafe())
+        .registerTypeHierarchyAdapter(Namespace::class.java, NamespaceTypeAdapter().nullSafe())
+        .registerTypeAdapter(WikiSite::class.java, WikiSiteTypeAdapter().nullSafe())
+        .registerTypeAdapterFactory(PostProcessingTypeAdapter())
+        .create()
+
+    @Before
+    @Throws(Throwable::class)
+    override fun setUp() {
+        super.setUp()
+
+        apiService = Retrofit.Builder()
+            .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
+            .addConverterFactory(GsonConverterFactory.create(gson))
+            .baseUrl(server().url)
+            .build()
+            .create(LoginInterface::class.java)
+    }
+
+    @Test
+    @Throws(Throwable::class)
+    fun testRequestSuccess() {
+        enqueueFromFile("user_extended_info.json")
+
+        apiService!!.getUserInfo("USER").subscribe(observer)
+
+        observer
+            .assertComplete()
+            .assertNoErrors()
+            .assertValue { result: MwQueryResponse ->
+                result.query()!!
+                    .userInfo()!!.id() == 24531888 && result.query()!!.getUserResponse("USER")!!
+                    .name() == "USER"
+            }
+    }
+
+    @Test
+    fun testRequestResponse404() {
+        enqueue404()
+
+        apiService!!.getUserInfo("USER").subscribe(observer)
+
+        observer.assertError(Exception::class.java)
+    }
+
+    @Test
+    fun testRequestResponseMalformed() {
+        enqueueMalformed()
+
+        apiService!!.getUserInfo("USER").subscribe(observer)
+
+        observer.assertError(MalformedJsonException::class.java)
+    }
+}