code: public static Token generate(final Random random, final Key key, final String plainText) {
          return generate(random, key, plainText.getBytes(charset));
      }
docs: Convenience method to generate a new Fernet token with a string payload.
  
  @param random a source of entropy for your application
  @param key the secret key for encrypting <em>plainText</em> and signing the token
  @param plainText the payload to embed in the token
  @return a unique Fernet token