code: public static String ofStreamInScope(String scopeName, String streamName) {
          Exceptions.checkNotNullOrEmpty(streamName, "streamName");
          return String.format("%s/%s", ofStreamsInScope(scopeName), streamName);
      }
docs: Creates a resource representation for use in authorization of actions pertaining to the specified stream within
  the specified scope.
  
  @param scopeName the name of the scope
  @param streamName the name of the stream
  @return a string representing the specified stream within the specified scope
  @throws NullPointerException if {@code scopeName} or {@code streamName} are null
  @throws IllegalArgumentException if {@code scopeName} or {@code streamName} are empty