Add api, ad login page, add models, views  

for postgres db in heroku:
 heroku addons:add heroku-postgresql:dev
 heroku pg:promote HEROKU_POSTGRESQL_COLOR
then run python in heroku:
 heroku run python

>>> from saulify import db
>>> db.create_all()

for add user:
>>> from saulify.models import User
>>> user = User(username='saul', email='saul@saulify.me')
>>> user.hash_password('saul')
>>> db.session.add(user)
>>> db.session.commit()

for login go to https://yourdomain/login

you can try here: https://mel-saulify.herokuapp.com/login
It should be better (imho) these routes be namespaces under /user, /user/apikey ?