add additional qs and header to http client; add additional queryParams to websocket

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

@@ -33,11 +33,14 @@ class StreamHttpClient {
       ..options.baseUrl = _options.baseUrl
       ..options.receiveTimeout = _options.receiveTimeout.inMilliseconds
       ..options.connectTimeout = _options.connectTimeout.inMilliseconds
-      ..options.queryParameters = {'api_key': apiKey}
+      ..options.queryParameters = {
+        'api_key': apiKey,
+        ..._options.queryParams,
+      }
       ..options.headers = {
         'Content-Type': 'application/json',
-        'X-Stream-Client': _options.userAgent,
         'Content-Encoding': 'application/gzip',
+        ..._options.headers,
       }
       ..interceptors.addAll([
         if (tokenManager != null) AuthInterceptor(this, tokenManager),

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

@@ -10,6 +10,8 @@ class StreamHttpClientOptions {
     this.location,
     this.connectTimeout = const Duration(seconds: 6),
     this.receiveTimeout = const Duration(seconds: 6),
+    this.queryParams = const {},
+    this.headers = const {},
   }) : _baseUrl = baseUrl ?? _defaultBaseURL;
 
   final String _baseUrl;
@@ -32,8 +34,20 @@ class StreamHttpClientOptions {
   /// received timeout, default to 6s
   final Duration receiveTimeout;
 
-  /// Get the current user agent
-  String get userAgent => 'stream-chat-dart-client-'
-      '${CurrentPlatform.name}-'
-      '${PACKAGE_VERSION.split('+')[0]}';
+  /// Common query parameters.
+  ///
+  /// List values use the default [ListFormat.multiCompatible].
+  ///
+  /// The value can be overridden per parameter by adding a [MultiParam]
+  /// object wrapping the actual List value and the desired format.
+  final Map<String, Object?> queryParams;
+
+  /// Http request headers.
+  /// The keys of initial headers will be converted to lowercase,
+  /// for example 'Content-Type' will be converted to 'content-type'.
+  ///
+  /// The key of Header Map is case-insensitive
+  /// eg: content-type and Content-Type are
+  /// regard as the same key.
+  final Map<String, Object?> headers;
 }