feat: Add tests, update notes implementation

packages/paperless_api/test/api/authentication/login_test.dart

@@ -0,0 +1,90 @@
+import 'package:dio/dio.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:http_mock_adapter/http_mock_adapter.dart';
+import 'package:mockito/mockito.dart';
+import 'package:paperless_api/paperless_api.dart';
+
+void main() {
+  group('AuthenticationApi with DioHttpErrorIncerceptor', () {
+    late PaperlessAuthenticationApi authenticationApi;
+    late DioAdapter mockAdapter;
+    const token = "abcde";
+    const invalidCredentialsServerMessage =
+        "Unable to log in with provided credentials.";
+
+    setUp(() {
+      final dio = Dio()..interceptors.add(DioHttpErrorInterceptor());
+      authenticationApi = PaperlessAuthenticationApiImpl(dio);
+      mockAdapter = DioAdapter(dio: dio);
+      // Valid credentials
+      mockAdapter.onPost(
+        "/api/token/",
+        data: {
+          "username": "username",
+          "password": "password",
+        },
+        (server) => server.reply(200, {"token": token}),
+      );
+      // Invalid credentials
+      mockAdapter.onPost(
+        "/api/token/",
+        data: {
+          "username": "wrongUsername",
+          "password": "wrongPassword",
+        },
+        (server) => server.reply(400, {
+          "non_field_errors": [invalidCredentialsServerMessage]
+        }),
+      );
+    });
+
+    // tearDown(() {});
+    test(
+      'should return a valid token when logging in with valid credentials',
+      () {
+        expect(
+          authenticationApi.login(
+            username: "username",
+            password: "password",
+          ),
+          completion(token),
+        );
+      },
+    );
+
+    test(
+      'should throw a PaperlessFormValidationException containing a reason '
+      'when logging in with invalid credentials',
+      () {
+        expect(
+          authenticationApi.login(
+            username: "wrongUsername",
+            password: "wrongPassword",
+          ),
+          throwsA(isA<PaperlessFormValidationException>().having(
+            (e) => e.unspecificErrorMessage(),
+            "non-field specific error message",
+            equals(invalidCredentialsServerMessage),
+          )),
+        );
+      },
+    );
+
+    test(
+      'should return an error when logging in with invalid credentials',
+      () {
+        expect(
+          authenticationApi.login(
+            username: "wrongUsername",
+            password: "wrongPassword",
+          ),
+          throwsA(isA<PaperlessFormValidationException>().having(
+            (e) => e.unspecificErrorMessage(),
+            "non-field specific error message",
+            equals(invalidCredentialsServerMessage),
+          )),
+        );
+      },
+    );
+  });
+}