/// <summary>
 /// Gets available API keys, whether they are enabled or not, optionally filtered by name.
 /// </summary>
 /// <param name="filter">Optional name filter.</param>
 /// <returns>Returns matching API keys.</returns>
 public async Task <IEnumerable <ApiKey> > GetApiKeys(string filter = null)
 {
     if (filter == null)
     {
         return(await ApiKeyRepository.GetApiKeys());
     }
     else
     {
         return(await ApiKeyRepository.SearchApiKeysByName(filter));
     }
 }