Save login credentials in local storage

Squashed commit of the following:

commit b480676cef
Author: Arne Schlüter <arne@schlueter.is>
Date:   Wed May 30 18:38:40 2018 +0200

    Remember login credentials

commit ed060e55b6
Author: Arne Schlüter <arne@schlueter.is>
Date:   Wed May 30 14:45:11 2018 +0200

    Add tests for auth process

commit ca8972f8c3
Author: Arne Schlüter <arne@schlueter.is>
Date:   Wed May 30 13:34:38 2018 +0200

    Make sure to always run tests in development

test/cljs/airsonic_ui/events_test.cljs

@@ -0,0 +1,29 @@
+(ns airsonic-ui.events-test
+  (:require [cljs.test :refer [deftest testing is]]
+            [clojure.string :as str]
+            [airsonic-ui.events :as events]))
+
+(enable-console-print!)
+
+(deftest authentication
+  (testing "Credential verification"
+    (let [server "https://localhost"
+          fx (events/authenticate {:db {}} [:_ "user" "pass" server])
+          request (:http-xhrio fx)]
+      (testing "uses correct server url"
+        (is (str/starts-with? (:uri request) server))
+        (is (str/includes? (:uri request) "/ping")))
+      (testing "saves the given server location"
+        (is (= server (get-in fx [:db :credentials :server]))))
+      (testing "invokes correct success callback"
+        (is (= ::events/credentials-verified (first (:on-success request)))))))
+  (testing "On succesfull response"
+    (let [fx (events/credentials-verified {:db {}} [:_ "user" "pass"])
+          credentials {:u "user" :p "pass"}]
+      (testing "credentials are sent to the router for access rights"
+        (is (= credentials (:routes/set-credentials fx))))
+      (testing "credentials are saved in the global state"
+        (is (= credentials (-> (get-in fx [:db :credentials])
+                               (select-keys [:u :p])))))
+      (testing "the login process is finalized"
+        (is (= [::events/logged-in] (:dispatch fx)))))))