Encrypt tokens in db

Eg https://stackoverflow.com/questions/17201450/salt-and-hash-password-in-nodejs-w-crypto/17201493#17201493

Advice from Liviu:

• New api keys can be uuid - check which library we use, don't use time as seed
• Show only once (TBD)
• Store hash and salt,
  • hash: salt+api_key, use something like sha256