chore: Move auth object passing to external msc implementations

lib/msc_extensions/msc_2835_uia_login/msc_2835_uia_login.dart

@@ -0,0 +1,49 @@
+library msc_2835_uia_login;
+
+import 'dart:convert';
+
+import 'package:http/http.dart' hide Client;
+import 'package:matrix/matrix.dart';
+
+extension UiaLogin on Client {
+  /// Implementation of MSC2835:
+  /// https://github.com/Sorunome/matrix-doc/blob/soru/uia-on-login/proposals/2835-uia-on-login.md
+  Future<LoginResponse> uiaLogin(
+    LoginType type, {
+    String? address,
+    String? deviceId,
+    AuthenticationIdentifier? identifier,
+    String? initialDeviceDisplayName,
+    String? medium,
+    String? password,
+    String? token,
+    String? user,
+    AuthenticationData? auth,
+  }) async {
+    final requestUri = Uri(path: '_matrix/client/v3/login');
+    final request = Request('POST', baseUri!.resolveUri(requestUri));
+    request.headers['content-type'] = 'application/json';
+    request.bodyBytes = utf8.encode(jsonEncode({
+      if (address != null) 'address': address,
+      if (deviceId != null) 'device_id': deviceId,
+      if (identifier != null) 'identifier': identifier.toJson(),
+      if (initialDeviceDisplayName != null)
+        'initial_device_display_name': initialDeviceDisplayName,
+      if (medium != null) 'medium': medium,
+      if (password != null) 'password': password,
+      if (token != null) 'token': token,
+      'type': {
+        LoginType.mLoginPassword: 'm.login.password',
+        LoginType.mLoginToken: 'm.login.token'
+      }[type]!,
+      if (user != null) 'user': user,
+      if (auth != null) 'auth': auth.toJson(),
+    }));
+    final response = await httpClient.send(request);
+    final responseBody = await response.stream.toBytes();
+    if (response.statusCode != 200) unexpectedResponse(response, responseBody);
+    final responseString = utf8.decode(responseBody);
+    final json = jsonDecode(responseString);
+    return LoginResponse.fromJson(json);
+  }
+}

lib/src/client.dart

@@ -451,7 +451,6 @@ class Client extends MatrixApi {
     String? token,
     String? deviceId,
     String? initialDeviceDisplayName,
-    AuthenticationData? auth,
     @Deprecated('Deprecated in favour of identifier.') String? user,
     @Deprecated('Deprecated in favour of identifier.') String? medium,
     @Deprecated('Deprecated in favour of identifier.') String? address,