Add authentication model to API

[dbuchwald]

User API must support authentication

[dbuchwald]

Added API operation for login, sample usage:

curl -X POST
http://localhost:3000/api/v1/login
-H 'Accept: application/json'
-H 'Cache-Control: no-cache'
-H 'Content-Type: application/json'
-H 'Postman-Token: 679f6ccf-81da-4682-8529-95ea578e7128'
-d '{
"id": 2242,
"password": "8d969eef6ecad3c29a3a629280e686cf0c3f5d5a86aff3ca12020c923adc6c92"
}'