use a static map for additional headers

packages/stream_chat/lib/src/client/client.dart

@@ -25,6 +25,7 @@ import 'package:stream_chat/src/core/models/member.dart';
 import 'package:stream_chat/src/core/models/message.dart';
 import 'package:stream_chat/src/core/models/own_user.dart';
 import 'package:stream_chat/src/core/models/user.dart';
+import 'package:stream_chat/src/core/platform_detector/platform_detector.dart';
 import 'package:stream_chat/src/core/util/utils.dart';
 import 'package:stream_chat/src/db/chat_persistence_client.dart';
 import 'package:stream_chat/src/event_type.dart';
@@ -126,6 +127,12 @@ class StreamChatClient {
     _originalChatPersistenceClient = value;
   }
 
+  static String defaultUserAgent = 'stream-chat-dart-client-'
+      '${CurrentPlatform.name}-'
+      '${PACKAGE_VERSION.split('+')[0]}';
+
+  static Map<String, Object?> additionalHeaders = {};
+
   ChatPersistenceClient? _originalChatPersistenceClient;
 
   /// Chat persistence client

packages/stream_chat/lib/src/core/http/interceptor/additional_headers_interceptor.dart

@@ -0,0 +1,17 @@
+import 'package:dio/dio.dart';
+import 'package:stream_chat/stream_chat.dart';
+
+/// Interceptor that sets additional headers for all requests.
+class AdditionalHeadersInterceptor extends Interceptor {
+  @override
+  Future<void> onRequest(
+    RequestOptions options,
+    RequestInterceptorHandler handler,
+  ) async {
+    options.headers = {
+      ...options.headers,
+      ...StreamChatClient.additionalHeaders,
+    };
+    return handler.next(options);
+  }
+}

packages/stream_chat/lib/src/core/http/interceptor/user_agent_interceptor.dart

@@ -1,20 +0,0 @@
-import 'package:dio/dio.dart';
-import 'package:stream_chat/src/core/platform_detector/platform_detector.dart';
-import 'package:stream_chat/version.dart';
-
-/// User agent interceptor that sets the user agent header
-class UserAgentInterceptor extends Interceptor {
-  final _defaultUserAgent = 'stream-chat-dart-client-'
-      '${CurrentPlatform.name}-'
-      '${PACKAGE_VERSION.split('+')[0]}';
-
-  @override
-  Future<void> onRequest(
-    RequestOptions options,
-    RequestInterceptorHandler handler,
-  ) async {
-    options.headers['X-Stream-Client'] =
-        '$_defaultUserAgent-${usedPackage.name}';
-    return handler.next(options);
-  }
-}

packages/stream_chat/lib/src/core/http/stream_http_client.dart

@@ -8,7 +8,7 @@ import 'package:stream_chat/src/core/http/connection_id_manager.dart';
 import 'package:stream_chat/src/core/http/interceptor/auth_interceptor.dart';
 import 'package:stream_chat/src/core/http/interceptor/connection_id_interceptor.dart';
 import 'package:stream_chat/src/core/http/interceptor/logging_interceptor.dart';
-import 'package:stream_chat/src/core/http/interceptor/user_agent_interceptor.dart';
+import 'package:stream_chat/src/core/http/interceptor/additional_headers_interceptor.dart';
 import 'package:stream_chat/src/core/http/stream_chat_dio_error.dart';
 import 'package:stream_chat/src/core/http/token_manager.dart';
 import 'package:stream_chat/src/location.dart';
@@ -42,7 +42,7 @@ class StreamHttpClient {
         ..._options.headers,
       }
       ..interceptors.addAll([
-        UserAgentInterceptor(),
+        AdditionalHeadersInterceptor(),
         if (tokenManager != null) AuthInterceptor(this, tokenManager),
         if (connectionIdManager != null)
           ConnectionIdInterceptor(connectionIdManager),

packages/stream_chat/lib/version.dart

@@ -1,22 +1,10 @@
 import 'package:stream_chat/src/client/client.dart';
-import 'package:stream_chat/src/core/platform_detector/platform_detector.dart';
 
 /// Current package version
 /// Used in [StreamChatClient] to build the `x-stream-client` header
 // ignore: constant_identifier_names
 const PACKAGE_VERSION = '3.2.0';
 
-/// Default user agent used for the 'x-stream-client' header
-final defaultUserAgent = 'stream-chat-dart-client-'
-    '${CurrentPlatform.name}-'
-    '${PACKAGE_VERSION.split('+')[0]}';
-
-/// Current used package
-/// This is used to set the `x-stream-client` header using info about
-/// the package in use
-/// For example: llc/core/ui
-Package usedPackage = Package.llc;
-
 /// Possible packages
 enum Package {
   /// The Low Level Client