Implement authentication properly

[ahderman]

Context

What is currently implemented:

• Username and password are hard-coded in the backend
• Nothing is stored in a database: neither username nor password nor session ids

This issue is about making sure that the username and password are stored in a database.

Acceptance criteria

• The following are stored in a Dynamo DB table of users:
  • username,
  • salt
  • number of iterations of the hashing algorithm
  • hashed(password+salt)
• The hashing algorithm is bcrypt (https://www.npmjs.com/package/bcryptjs)
• On login, the provided password is checked against stored values using the same bcryptjs library.