Title: Authenticate
Scope: Authentication
Level: User Goal
Actors: Anonymous user
Brief: Any not logged in user can authenticate to the service.

Precondition: Website opened
Main success scenario: User successfully authenticates against the server. The websites changes its state to authenticated, which enables more features (e.g. creation of snippets).
Alternative scenario: The authentication was not successful (e.g. wrong credentials). The user is prompted to check his credentials and retry.
Error scenario: Technical problems prevent the authentication from succeeding (e.g. connection issues). The user is informed about the issue.
Postcondition: Website is in authenticated state, meaning that all subsequent requests will use the authentication token to identify to the server.
Non-functional Constraints:
- Security mechanism
- Is precondition to use other functions