block13.js

// server/src/graphql/videoApi.js
...
const joinSession = async (_, { uuid }, __, ___) => {
  // check if a uuid has been provided
  if (!uuid) {
    throw new Error(INTERNAL_ERROR);
  }

  // Retrieve the session from the database
  const [videocall] = videocalls.filter(videocall => videocall.uuid === uuid);

  // initialize the opentok client
  initializeOpentok();

  // generating the token
  const token = generateToken(videocall.sessionId);

  // 
  return {
    uuid,
    token,
    session: videocall.sessionId,
    apiKey
  };
};
...