code: protected void processUpgradeHeaderSettings(String settings) throws Http2Exception {
  
          if (settings != null) {
              byte[] decoded = decode(settings);
              if (decoded != null) {
                  FrameSettings settingsFrame = new FrameSettings(0, decoded.length, (byte) 0x0, false, FrameDirection.READ);
                  settingsFrame.processPayload(decoded);
                  updateSettings(settingsFrame);
              }
          }
      }
docs: A settings frame can be encoded as a base-64 string and passed as a header on the initial upgrade request.
  This method decodes that base-64 string and applies the encoded settings to this http2 connection.