fix(web): fix Theme Custom CSS endpoint requiring the user to be logged in as the server admin (#4633)

* fix custom css requiring the user to be the admin and logged in

* move theme api to custom endpoint

* add e2e test

mobile/openapi/lib/api.dart

@@ -145,6 +145,7 @@ part 'model/server_info_response_dto.dart';
 part 'model/server_media_types_response_dto.dart';
 part 'model/server_ping_response.dart';
 part 'model/server_stats_response_dto.dart';
+part 'model/server_theme_dto.dart';
 part 'model/server_version_response_dto.dart';
 part 'model/shared_link_create_dto.dart';
 part 'model/shared_link_edit_dto.dart';

mobile/openapi/lib/api/server_info_api.dart

@@ -262,6 +262,47 @@ class ServerInfoApi {
     return null;
   }
 
+  /// Performs an HTTP 'GET /server-info/theme' operation and returns the [Response].
+  Future<Response> getThemeWithHttpInfo() async {
+    // ignore: prefer_const_declarations
+    final path = r'/server-info/theme';
+
+    // ignore: prefer_final_locals
+    Object? postBody;
+
+    final queryParams = <QueryParam>[];
+    final headerParams = <String, String>{};
+    final formParams = <String, String>{};
+
+    const contentTypes = <String>[];
+
+
+    return apiClient.invokeAPI(
+      path,
+      'GET',
+      queryParams,
+      postBody,
+      headerParams,
+      formParams,
+      contentTypes.isEmpty ? null : contentTypes.first,
+    );
+  }
+
+  Future<ServerThemeDto?> getTheme() async {
+    final response = await getThemeWithHttpInfo();
+    if (response.statusCode >= HttpStatus.badRequest) {
+      throw ApiException(response.statusCode, await _decodeBodyBytes(response));
+    }
+    // When a remote server returns no body with a status of 204, we shall not decode it.
+    // At the time of writing this, `dart:convert` will throw an "Unexpected end of input"
+    // FormatException when trying to decode an empty string.
+    if (response.body.isNotEmpty && response.statusCode != HttpStatus.noContent) {
+      return await apiClient.deserializeAsync(await _decodeBodyBytes(response), 'ServerThemeDto',) as ServerThemeDto;
+    
+    }
+    return null;
+  }
+
   /// Performs an HTTP 'GET /server-info/ping' operation and returns the [Response].
   Future<Response> pingServerWithHttpInfo() async {
     // ignore: prefer_const_declarations

mobile/openapi/lib/api_client.dart

@@ -381,6 +381,8 @@ class ApiClient {
           return ServerPingResponse.fromJson(value);
         case 'ServerStatsResponseDto':
           return ServerStatsResponseDto.fromJson(value);
+        case 'ServerThemeDto':
+          return ServerThemeDto.fromJson(value);
         case 'ServerVersionResponseDto':
           return ServerVersionResponseDto.fromJson(value);
         case 'SharedLinkCreateDto':

mobile/openapi/lib/model/server_theme_dto.dart

@@ -0,0 +1,98 @@
+//
+// AUTO-GENERATED FILE, DO NOT MODIFY!
+//
+// @dart=2.12
+
+// ignore_for_file: unused_element, unused_import
+// ignore_for_file: always_put_required_named_parameters_first
+// ignore_for_file: constant_identifier_names
+// ignore_for_file: lines_longer_than_80_chars
+
+part of openapi.api;
+
+class ServerThemeDto {
+  /// Returns a new [ServerThemeDto] instance.
+  ServerThemeDto({
+    required this.theme,
+  });
+
+  SystemConfigThemeDto theme;
+
+  @override
+  bool operator ==(Object other) => identical(this, other) || other is ServerThemeDto &&
+     other.theme == theme;
+
+  @override
+  int get hashCode =>
+    // ignore: unnecessary_parenthesis
+    (theme.hashCode);
+
+  @override
+  String toString() => 'ServerThemeDto[theme=$theme]';
+
+  Map<String, dynamic> toJson() {
+    final json = <String, dynamic>{};
+      json[r'theme'] = this.theme;
+    return json;
+  }
+
+  /// Returns a new [ServerThemeDto] instance and imports its values from
+  /// [value] if it's a [Map], null otherwise.
+  // ignore: prefer_constructors_over_static_methods
+  static ServerThemeDto? fromJson(dynamic value) {
+    if (value is Map) {
+      final json = value.cast<String, dynamic>();
+
+      return ServerThemeDto(
+        theme: SystemConfigThemeDto.fromJson(json[r'theme'])!,
+      );
+    }
+    return null;
+  }
+
+  static List<ServerThemeDto> listFromJson(dynamic json, {bool growable = false,}) {
+    final result = <ServerThemeDto>[];
+    if (json is List && json.isNotEmpty) {
+      for (final row in json) {
+        final value = ServerThemeDto.fromJson(row);
+        if (value != null) {
+          result.add(value);
+        }
+      }
+    }
+    return result.toList(growable: growable);
+  }
+
+  static Map<String, ServerThemeDto> mapFromJson(dynamic json) {
+    final map = <String, ServerThemeDto>{};
+    if (json is Map && json.isNotEmpty) {
+      json = json.cast<String, dynamic>(); // ignore: parameter_assignments
+      for (final entry in json.entries) {
+        final value = ServerThemeDto.fromJson(entry.value);
+        if (value != null) {
+          map[entry.key] = value;
+        }
+      }
+    }
+    return map;
+  }
+
+  // maps a json object with a list of ServerThemeDto-objects as value to a dart map
+  static Map<String, List<ServerThemeDto>> mapListFromJson(dynamic json, {bool growable = false,}) {
+    final map = <String, List<ServerThemeDto>>{};
+    if (json is Map && json.isNotEmpty) {
+      // ignore: parameter_assignments
+      json = json.cast<String, dynamic>();
+      for (final entry in json.entries) {
+        map[entry.key] = ServerThemeDto.listFromJson(entry.value, growable: growable,);
+      }
+    }
+    return map;
+  }
+
+  /// The list of required keys that must be present in a JSON.
+  static const requiredKeys = <String>{
+    'theme',
+  };
+}
+