added user model

front-api/controllers/user.rb

@@ -0,0 +1,20 @@
+get '/user/auth' do
+  # TODO: do something that makes sense here
+  res = User.find_by(id: 1).try(:authenticate, 'spassword')      # => false
+  res.to_json
+end
+
+post '/user' do
+  request.body.rewind
+  json = request.body.read
+
+  user = User.new()
+  user.from_json(json, false)
+
+  if user.save
+    "ok"
+  else
+    status 400
+    user.errors.to_json
+  end
+end