Token auth (#434)

* Embed device platform information into token request

* Remove username and password from userProfile

* Display icon to show if profile has associated user token

* Remove username / password from login settings screen

* Refactor login procedure around token auth

* Refactoring

* Add profile login screen

- Username / password values are not stored
- Just to fetch api token

* Login with basic auth

* Pass profile to API when connecting

* Remove _BASE_URL accessor

- Fixes URL caching bug

* Add more context to login screen

* Add helper functions for unit tests

- Change default port to 8000 (makes testing easier with local inventree instance)

* api.dart handles basic auth now

* fix api_test.dart

* Further test improvements

* linting fixes

* Provide feedback when login fails

* More linting

* Record user details on login, and display in "about" widget

* Fix string lookup

* Add extra debug

* Fix auth values

* Fix user profile test

lib/settings/about.dart

@@ -96,10 +96,18 @@ class InvenTreeAboutWidget extends StatelessWidget {
           )
       );
 
+      tiles.add(
+        ListTile(
+          title: Text(L10().username),
+          subtitle: Text(InvenTreeAPI().username),
+          leading: InvenTreeAPI().username.isNotEmpty ? FaIcon(FontAwesomeIcons.user) : FaIcon(FontAwesomeIcons.userSlash, color: COLOR_DANGER),
+        )
+      );
+
       tiles.add(
         ListTile(
           title: Text(L10().version),
-          subtitle: Text(InvenTreeAPI().version.isNotEmpty ? InvenTreeAPI().version : L10().notConnected),
+          subtitle: Text(InvenTreeAPI().serverVersion.isNotEmpty ? InvenTreeAPI().serverVersion : L10().notConnected),
           leading: FaIcon(FontAwesomeIcons.circleInfo),
         )
       );
@@ -107,13 +115,13 @@ class InvenTreeAboutWidget extends StatelessWidget {
       tiles.add(
         ListTile(
           title: Text(L10().serverInstance),
-          subtitle: Text(InvenTreeAPI().instance.isNotEmpty ? InvenTreeAPI().instance : L10().notConnected),
+          subtitle: Text(InvenTreeAPI().serverInstance.isNotEmpty ? InvenTreeAPI().serverInstance : L10().notConnected),
           leading: FaIcon(FontAwesomeIcons.server),
         )
       );
 
       // Display extra tile if the server supports plugins
-      if (InvenTreeAPI().pluginsEnabled()) {
+      if (InvenTreeAPI().pluginsEnabled) {
         tiles.add(
           ListTile(
             title: Text(L10().pluginSupport),