public ClientProxyConfiguration(ClientProxyConfiguration existing)
     : this (port: existing?.Port,
           host: existing?.Host,
           username: existing?.Username,
           password: existing?.Password)
 {
 }
 public ClientConfiguration(
     ClientApiKeyConfiguration apiKey = null,
     ClientCacheManagerConfiguration cacheManager = null,
     string baseUrl = null,
     int? connectionTimeout = null,
     ClientAuthenticationScheme? authenticationScheme = null,
     ClientProxyConfiguration proxy = null)
 {
     this.ApiKey = new ClientApiKeyConfiguration(apiKey) ?? Default.Configuration.Client.ApiKey;
     this.CacheManager = new ClientCacheManagerConfiguration(cacheManager) ?? Default.Configuration.Client.CacheManager;
     this.BaseUrl = baseUrl ?? Default.Configuration.Client.BaseUrl;
     this.ConnectionTimeout = connectionTimeout ?? Default.Configuration.Client.ConnectionTimeout;
     this.AuthenticationScheme = authenticationScheme ?? Default.Configuration.Client.AuthenticationScheme;
     this.Proxy = new ClientProxyConfiguration(proxy) ?? Default.Configuration.Client.Proxy;
 }